- freely available
Int. J. Mol. Sci. 2012, 13(8), 10387-10400; doi:10.3390/ijms130810387
Published: 21 August 2012
Abstract: Mucin 16 (MUC16) is a type I transmembrane protein, the extracellular portion of which is shed after proteolytic degradation and is denoted as CA125 antigen, a well known tumor marker for ovarian cancer. Regarding its polypeptide and glycan structures, as yet there is no detailed insight into their heterogeneity and ligand properties, which may greatly influence its function and biomarker potential. This study was aimed at obtaining further insight into the biological capacity of MUC16/CA125, using in silico analysis of corresponding mucin sequences, including similarity searches as well as GO (gene ontology)-based function prediction. The results obtained pointed to the similarities within extracellular serine/threonine rich regions of MUC16 to sequences of proteins expressed in evolutionary distant taxa, all having in common an annotated role in adhesion-related processes. Specifically, a homology to conserved domains from the family of herpesvirus major outer envelope protein (BLLF1) was found. In addition, the possible involvement of MUC16/CA125 in carbohydrate-binding interactions or cellular transport of protein/ion was suggested.
Mucins comprise a family of secreted or transmembrane proteins, characterized by extensive O-glycosylation on multiple tandem repeats of proline/threonine/serine rich (PTS) amino acid sequences [1–4]. Owing to their structural specificities, mucins contribute to mucociliary defense, acting as physical and chemical barriers, and to innate immune defense as part of signal transduction pathways [5–9].
Mucin 16 (MUC16) is a type I transmembrane protein, the extracellular portion of which is shed after proteolytic degradation. This is denoted as CA125 antigen, a well known tumor marker for ovarian cancer [10–12]. It is placed in the mucin family according to the results of partial cloning of sequence, but due to its specific properties, such as N-glycan composition, MUC16 does not fit well into either class of mucin molecules [13–15]. It has an extremely long amino acid sequence, and the available data indicate that this is dominated by 56 SEA (sea urchin sperm protein, enterokinase, agrin) repeats and 2 ANK (ankyrin) repeats, which occur in diverse functionally different proteins . SEA is an extracellular domain associated with O-glycosylation, which might regulate or assist binding to neighboring carbohydrate moieties . The ankyrin repeats are tandemly repeated modules of about 33 amino acids, which are one of the most common protein–protein interaction motifs . Regarding its polypeptide and glycan structures, as yet there is no detailed insight into their heterogeneity and ligand properties, which may greatly influence the function and biomarker potential of MUC16/CA125 [19–23].
This study was aimed at gaining more insight into the biological capacity of this mucin by exploiting a combination of computational and experimental approaches. Thus, we performed in silico analysis of corresponding mucin sequences, including similarity searches as well as GO (gene ontology)-based function prediction. Subsequently, selected computationally identified hits were experimentally validated based on CA125-immunoreactivity.
The results obtained pointed to similarities within extracellular serine/threonine (Ser/Thr) rich regions of Muc16 to protein sequences expressed in evolutionary distant taxa, as well as homology to conserved domains, all having in common an annotated role in adhesion-related processes.
2. Results and Discussion
Table 1 lists the highest scoring candidates (putative/uncharacterized protein hits not considered) obtained when the MUC16/CA125 sequence was submitted to BLAST similarity searches through the following protein databases: virus, bacteria, fungi, eukaryota.
The membrane glycoprotein (039781)/glycoprotein gp2 (Q6SV6W0) from Equine herpesvirus 1 as well as glycoprotein gp350-220 (E2GKY4) from Epstein Barr virus (EBV) were reported as viral hits exhibiting sequence similarity to the target sequence. Human and animal herpesviruses are large, enveloped virions with related glycoproteins incorporated into the virion envelope. Conservation is manifested at both the structural and functional level. Gp2 is a virion membrane protein involved in viral reproduction [24–26]. Gp350-220 is the most abundantly expressed part of the viral envelope and its binding to CD21 is an essential step in infection of B lymphocytes by the EBV [27–29].
Cell wall surface anchor family protein (B2ISC7/Q97P71) from Streptococcus pneumoniae and serine-rich adhesin for platelets (Q4L9P0) from Staphylococcus haemolyticus were reported as bacterial hits. GO annotation described these entries as having transmembrane transporter activity and virulence activity mediating binding to specific cells [30–33].
The search through the fungi database pointed to high scoring candidates, known to exhibit mucin-like properties: cell surface flocculin, Flo11 (E9P8M0) and Muc1p (C8ZAR8) from Saccharomyces cerevisiae. Ser/Thr rich regions in high scoring hits, are known to be involved in cell adhesion and pseudohyphal formation or binding to polysaccharides in the natural environment and/or efficient invasive growth on such substrates [34–39].
In addition, the search through the eukaryota database reported mucin-like proteophosphoglycan 5 (E9AEM9) from Leishmania major exhibiting similarity to MUC16. It belongs to a family of heterogeneous polypeptides of unusual composition and structure and is the major cell surface molecule of promastigotes known to mediate attachment to the vector . In addition, it is able to activate complement, but is poorly immunogenic and behaves immunologically like a carbohydrate .
Taken together, the results obtained put MUC16 in the context of evolutionary distant modular proteins sharing common features in terms of GO functional categories: cellular component (GO:0005575), biological processes (GO:0008150), and molecular function (GO:0003674). Thus, the highest scoring reported candidates are associated with the membrane/cell wall/extracellular region and are involved in different types of adhesion processes based on protein-protein or protein-sugar binding.
All reported similarities were found within the extracellular Ser/Thr-rich regions of MUC16, which are typical of mucin molecules in general. No relation to annotated domains from available databases appeared, except for gp2/BLLF1 (herpesvirus major outer envelope glycoprotein) from conserved domain database (CDD) . As already mentioned, BLLF1 (also termed gp 350/220) represents a major antigen responsible for production of neutralizing antibodies in vivo. Starting from these observations as well as reported data on elevated CA125 concentration in patients with different type of B cell lymphomas, which could be associated with EBV infection [43,44], anti-human CA125 antibodies were probed for reactivity with herpesviruses glycoproteins. Thus, EBV capsid antigen and HSV 1 antigen were probed with two classes of monoclonal antibodies to MUC16/CA125: OC125/OC125-like and M11/M11-like, reacting mainly with the repeated peptide sequences [13,14,45].
In a solid phase binding assay with immobilized targets (Figure 1), OC125-like antibody, but not M11-like antibody, gave a signal above background indicating measurable reactivity to EBV CA, but it was weak relative to the reaction with CA125. As for HSV 1 antigens, both antibodies gave measurable reactivity, being slightly higher for OC125-like antibody.
Generally, there is a phenomenon that unrelated organisms can have antigens in common [46–48]. Thus, it is well known that the agglutination test for EBV is based on the finding that it has an antigen in common with sheep and horse erythrocytes . Moreover, fungal antigen crossreactivity is reported between Candida species and human ovarian carcinoma , whereas crossreaction of Saccharomyces cerevisiae was found in the human colon i.e., in granulation tissue of inflamed colonic mucosa and peripheral leukocytes in patients with Crohns disease [50,51]. However, crude yeast extract, as a source of the identified mucin-like molecules, showed no trace of CA125-immunoreactivity (data not shown).
The available data indicate that 4% of 600 monoclonal antibodies against a large variety of viruses crossreacted with healthy host tissues and that heterologous immunity may be elicited even by very short common sequences (such as six amino acids) . The biological meaning of such crossreactivity i.e., heterologous immunity, in general, is not understood and also it is not known whether it may have any functional consequences.
As part of a strategy for assignment of structural/functional domains, a BLAST search starts with the basic assumption that higher sequence similarity increases confidence in function annotation transfer [53,54]. However, there is no threshold and homology does not always mean similar function. Thus, in addition to BLAST, protein function prediction software based on GO annotations were also used for computational analysis of CA125 sequence (Tables 2 and 3). Although, the reported matches had low probability scores, they put MUC16/CA125 in the context of modular proteins with an annotated role in adhesion-related processes. In terms molecular function, GO category: binding (GO:0005488) was associated with purine nucleotide (GO:0017076), metal ion/ion (GO:0046872/GO:0043197) or sugar binding (GO:0005529). The predicted sugar binding ability was related to 1,4-alpha-d-glucan (GO:0004339) and chitin (GO:0008061) [55,56]. In terms of biological processes, GO category: cellular process (GO:0009987) was associated with cell-matrix adhesion (GO:0007160), and GO category: physiological process (GO:0007582) was associated with cell growth (GO:0016049), transport (GO:0006810) and metabolism (GO:0008152). Thus, invasive growth (GO:0001403), cation transport (GO:0006812), i.e., ATP synthesis coupled proton transport (GO:0015986) and polysaccharide metabolism (GO:0000272), were annotated, respectively [57,58].
So far, several lines of experimental evidence obtained on cancer- or pregnancy-associated MUC16/CA125 antigen, indicate possible involvement in adhesive/anti-adhesive processes during cancer progression or embryonic development [59–62]. The precise mechanisms of these processes are not fully explained. Generally, it is suggested that there is link between cell adhesion and ion transport. For instance, local extracellular pH levels at tumor focal adhesion sites modulate the strength of cell adhesion i.e., more protons leads to tighter adhesion and decreased migration . These processes can involve different molecules, but there are data substantiating the existence of adhesion molecules with amino acid identity (40%) and immunologically cross-reactive to the beta subunit of Na/K-ATPase . It is speculated that adhesive or anti-adhesive properties of a particular molecule may result from its influence on different transducing systems in the form of an ion pump, channel or carrier .
In addition, they can be dependent on its glycosylation status. It is known that mucins as ligands for cell-cell adhesion molecules (CAM) or as CAM themselves are an important part of the adhesion interaction network based on carbohydrate-binding interactions. Indeed, the results obtained indicated distinct GO terms, whose annotations, refer to lectin- or lectin-like interactions.
In terms of biological processes, besides cellular processes, carbohydrate-binding is also supposed to be relevant for physiological processes such as invasive growth (GO:0001403) or substrate-bound cell migration (GO:0006929). Thus, flocculin, identified as one of the high scoring hits, is associated with fimbrialike structures and it is involved in invasion and filamentous growth . On the other hand, MUC16 was reported to be localized on the surface of uterodome (pinopode) protrusions of the endometrium, acting as a barrier for trophoblast adherence . Cell-matrix contact structures, i.e., cellular protrusions can be morphologically different, but mechanisms of spreading are thought to be similar in normal and pathologically altered cells . However, there are no data on flocculin or CA125 activities in terms of sugar-binding interactions.
MUC16 has a distinct evolutionary relationship with other transmembrane mucins. Using sequence comparison of well characterized mucin domains: SEA, NIDO, AMOP and VWD, it was shown that MUC16 evolved separately, before the divergence of birds and mammals . Thus, in contrast to the others, it has homology in non-mammalian species, based on the SEA domain. In this study, the starting point was modular organization and the preposition that sharing evolutionary conserved structural and functional motifs, other than those already known, can give us more information about its position in the human interactome.
Collectively, the results obtained direct further investigation of CA125 antigen towards collecting data to substantiate the involvement of common conserved protein motifs in functional activities of evolutionarily diversified molecules, as has emerged from this study.
3. Experimental Section
The protein sequence of human mucin 16 (MUC16) (ovarian cancer-related tumor marker CA125), accession number Q8WXI7 (UniProtKB, The Universal Protein Knowledgebase), accession number IPI00103552 (IPI, The International Protein Index), accession number NP_078966.2 (NCBI refSeq, National Center for Biotechnology Information Reference Sequence) was retrieved from public databases [68,69].
3.2. Similarity Search
The protein sequence of human mucin 16 (MUC16) was subjected to a similarity search in the Protein Knowledgebase (UniProtKB) using BLAST (Basic Local Alignment Search Tool) [70–72]. The following protein knowledgebases were searched: bacteria, viruses, fungi, eukaryota; and the highest scoring candidates were ranked under different parameter settings (threshold, matrix, filtering, gapped sequence).
3.3. Protein Function Prediction
Functions were assigned based on the homologues identified using protein function prediction servers: JAFA metaserver (Joined Assembly of Function Annotations) at http://jafa.burnham.org, PFP (Automated Protein Function Prediction) at http://dragon.bio.purdue.edu/pfp, and GO (GeneOntology) at http://www.geneontology.com, which gives a definition of functional context and provides machine-legible functional annotation [73–78].
3.4.1. Viral Antigens
Mouse monoclonal anti-human CA125 antibodies: clone X325 (M-11 like) and clone X306 (OC125-like) were from HyTest (PharmaCity, Turku, Finland). They were allowed to react with immobilized Epstein-Barr Virus (EBV) capsid antigens (CA), from Epstein-Barr Virus (EBV) VCA IgG kit (Virion/Serion GmbH, Wurzburg, Germany), or Herpes simplex virus type 1 (HSV 1) cell culture-derived antigens, from Herpes simplex virus type 1 IgG kit (Human GmbH, Wiesbaden, Germany). After incubation for 3 h at room temperature (RT), the wells were washed three times with 0.1 M PBS, pH 7.2 and biotinylated goat anti-mouse IgG (Vector Laboratories, Burlinghame, CA, USA) was added. Subsequent to incubation for 1 h, the wells were rinsed and Vectastain Elite ABC reagent (Vector Laboratories, Burlinghame, CA, USA) was added followed by incubation for 30 min. After another washing step, addition of TMB substrate solution and incubation for 10 min, the reaction was stopped with 0.16 M H2SO4. The absorbance was measured at 450 nm on a Wallac 1420 Multilabel Counter (Monza, Italy). In parallel, a control assay was performed with an irrelevant monoclonal anti-hCG IgG, clone 5008-SP-5 (Medix Biochemica, Kauniainen, Finland) to determine non-specific binding.
3.4.2. Crude Yeast (Saccharomyces cerevisiae) Extract
Serial dilutions of crude yeast (Saccharomyces cerevisiae) extract in 0.01 M carbonate buffer, pH 9.2, were adsorbed on polystyrene test tubes (Spektar, Cacak, Serbia) overnight at 4 °C. The tubes were then rinsed three times with 0.1 M PBS, pH 7.2, blocked with 1% casein for 2 h at RT and rinsed again three times with 0.1 M PBS, pH 7.2. Reaction with the corresponding monoclonal anti-human CA125-antibodies was then allowed as described for viral antigens.
Since protein function has many facets and is highly contextual, bioinformatic data on the predicted GO molecular function of CA125 can be considered in the light of possible general principles shared across distant distinct, yet related proteins. The results obtained suggested a possible correlation between the role of the serine/threonine rich domain of yeast, acting as a sensor for extracellular osmotic pressure and that of the mucin domain of transmembrane mucins in monitoring extracellular ion gradients and pH [35,79,80]. In addition, a possible relationship has emerged between mucin participation in polarized growth and directional motility i.e., amoeboid mechanisms of propulsion and mucin-like fungal proteins in pseudohyphal and filamentous growth involving sugar-substrate binding [81,82].
This work was supported by the Ministry for Education and Science of the Republic of Serbia, project code 173010.
- Conflict of InterestThe authors declare no financial or commercial conflict of interest.
- Gum, J.R. Mucin genes and proteins they encode: Structure, diversity and regulation. Am. J. Respir. Cell Mol. Biol 1992, 7, 557–564. [Google Scholar]
- Perez-Vilar, J.; Hill, R.L. Mucin Family of Glycoproteins. In Encyclopedia of Biological Chemistry; Lennarz, L., Ed.; Academic Press/Elsevier: Oxford, UK, 2004; Volume 2, pp. 758–764. [Google Scholar]
- Desseyn, J.L.; Tetaert, D.; Gouyer, V. Architecture of the large membrane-bound mucins. Gene 2008, 410, 215–222. [Google Scholar]
- Hattrup, C.L.; Gendler, S.J. Structure and function of the cell surface (tethered) mucins. Annu. Rev. Physiol 2008, 70, 431–457. [Google Scholar]
- Jonckheere, N.; van Seuningen, I. The membrane-bound mucins: From cell signalling to transcriptional regulation and expression in epithelial cancers. Biochimie 2009, 92, 1–11. [Google Scholar]
- Bafna, S.; Kaur, S.; Batra, S.K. Membrane-Bound mucins: The mechanistic basis for alterations in the growth and survival of cancer cells. Oncogene 2010, 29, 2893–2904. [Google Scholar]
- Palileo, C.; Kaunitz, J.D. Gastrointestinal defense mechanisms. Curr. Opin. Gastroenterol 2011, 27, 543–548. [Google Scholar]
- McGuckin, M.A.; Lindén, S.K.; Sutton, P.; Florin, T.H. Mucin dynamics and enteric pathogens. Nat. Rev. Microbiol 2011, 4, 265–278. [Google Scholar]
- Parker, D.; Prince, A. Innate immunity in the respiratory epithelium. Am. J. Respir. Cell Mol. Biol 2011, 45, 189–201. [Google Scholar]
- Montz, F.J. CA 125. In Serological Cancer Markers; Sell, S., Ed.; The Humana Press: Totowa, NJ, USA, 1992; pp. 417–425. [Google Scholar]
- Scholler, N.; Urban, N. CA 125 in ovarian cancer. Biomark. Med 2007, 1, 513–523. [Google Scholar]
- Perez, B.H.; Gipson, I.K. Focus on molecules: Human mucin MUC16. Exp. Eye Res 2008, 87, 400–401. [Google Scholar]
- Yin, B.W.; Lloyd, K.O. Molecular cloning of the CA 125 ovarian cancer antigen: Identification as a new mucin, MUC16. J. Biol. Chem 2001, 276, 27371–27375. [Google Scholar]
- O’Brien, T.J.; Beard, J.B.; Underwood, L.J.; Dennis, R.A.; Santin, A.D.; York, L. The CA 125 gene: An extracellular superstructure dominated by repeat sequences. Tumour Biol 2001, 22, 348–366. [Google Scholar]
- O’Brien, T.J.; Beard, J.B.; Underwood, L.J.; Shigemasa, K. The CA 125 gene: A newly discovered extension of the glycosylated N-terminal domain doubles the size of this extracellular superstructure. Tumour Biol 2002, 23, 154–169. [Google Scholar]
- Maeda, T.; Inoue, M.; Koshiba, S.; Yabuki, T.; Aoki, M.; Nunokawa, E.; Seki, E.; Matsuda, T.; Motoda, Y.; Kobayashi, A.; et al. Solution structure of the SEA domain from the murine homologue of ovarian cancer antigen CA 125 (MUC16). J. Biol. Chem 2004, 279, 13174–13182. [Google Scholar]
- IPR000082 SEA. Available online: http://www.ebi.ac.uk/interpro/IEntry?ac=IPR000082 accessed on 3 April 2012.
- Sedgwick, S.G.; Smerdon, S.J. The ankyrin repeat: A diversity of interactions on a common structural framework. Trends Biochem. Sci 1999, 24, 311–316. [Google Scholar]
- Wong, N.K.; Easton, R.L.; Pancio, M.; Sutton-Smith, M.; Morrison, J.C.; Lattanzio, F.A.; Moris, H.R.; Clark, G.F.; Dell, A.; Patankar, M.S. Characterization of the oligosaccharides associated with human ovarian tumor marker CA125. J. Biol. Chem 2003, 278, 28619–28634. [Google Scholar]
- Jankovic, M.; Tapuskovic, B. Molecular forms and microheterogeneity of the oligosaccharide chains of pregnancy-associated CA125 antigen. Hum. Reprod 2005, 20, 2632–2638. [Google Scholar]
- Jankovic, M.; Milutinovic, B. Glycoforms of CA125 antigen as possible cancer biomarker. Cancer Biomark 2008, 1, 1–8. [Google Scholar]
- Jankovic, M.M.; Milutinovic, B.S. Pregnancy-Associated CA125 antigen as mucin: Evaluation of ferning morphology. Mol. Hum. Reprod 2007, 13, 405–408. [Google Scholar]
- Bouanène, H.; Saibi, W.; Mokni, M.; Sriha, B.; Ben Fatma, L.; Ben Limem, H.; Ben Ahmed, S.; Gargouri, A.; Miled, A. Biochemical and morphological differences between CA125 isolated from healthy women and patients with epithelial ovarian cancer from Tunisian population. Pathol. Oncol. Res 2012, 18, 325–330. [Google Scholar]
- Whittaker, G.R.; Wheldon, L.A.; Giles, L.E.; Stocks, J.M.; Halliburton, I.W.; Killington, R.A.; Meredith, D.M. Characterization of the high Mr glycoprotein (gp300) of equine herpesvirus type 1 as a novel glycoprotein with extensive O-linked carbohydrate. J. Gen. Virol 1990, 71, 2416. [Google Scholar]
- Wellington, J.E.; Allen, G.P.; Gooley, A.A.; Love, D.N.; Packer, N.H.; Yan, J.X.; Whalley, J.M. The highly O-glycosylated glycoprotein gp2 of equine herpesvirus 1 is encoded by gene 71. J. Virol. 1996, 70, 8198. [Google Scholar]
- Learmonth, G.S.; Love, D.N.; Gilkerson, J.R.; Wellington, J.E.; Whalley, J.M. The C-terminal regions of the envelope glycoprotein gp2 of equine herpesvirus 1 and 4 are antigenically distinct. Arch. Virol 2002, 147, 607–615. [Google Scholar]
- Tanner, J.; Weis, J.; Fearon, D.; Whang, Y.; Kieff, E. Epstein-Barr virus gp350/220 binding to the B lymphocyte C3d receptor mediates adsorption, capping, and endocytosis. Cell 1987, 50, 203–213. [Google Scholar]
- Janz, A.; Oezel, M.; Kurzeder, C.; Mautner, J.; Pich, D.; Kost, M.; Hammerschmidt, W.; Delecluse, H.J. Infectious Epstein-Barr virus lacking major glycoprotein BLLF1 (gp350/220) demonstrates the existence of additional viral ligands. J. Virol 2000, 74, 10142–10152. [Google Scholar]
- Luo, B.; Liu, M.; Chao, Y.; Wang, Y.; Jing, Y.; Sun, Z. Characterization of Epstein-Barr virus gp350/220 gene variants in virus isolates from gastric carcinoma and nasopharyngeal carcinoma. Arch. Virol 2012, 157, 207–216. [Google Scholar]
- Cell wall surface anchor family protein, Available online: http://www.uniprot.org/uniprot/B2ISC7 accessed on 5 April 2012.
- Ding, F.; Tang, P.; Hsu, M.H.; Cui, P.; Hu, S.; Yu, J.; Chiu, C.H. Genome evolution driven by host adaptations results in a more virulent and antimicrobial-resistant Streptococcus pneumoniae serotype 14. BMC Genomics 2009, 10, 158. [Google Scholar]
- Serine-rich adhesin for platelets, Available online: http://www.uniprot.org/uniprot/Q4L9P0 accessed on 5 April 2012.
- Takeuchi, F.; Watanabe, S.; Baba, T.; Yuzawa, H.; Ito, T.; Morimoto, Y.; Kuroda, M.; Cui, L.; Takahashi, M.; Ankai, A.; et al. Whole-Genome sequencing of Staphylococcus haemolyticus uncovers the extreme plasticity of its genome and the evolution of human-colonizing staphylococcal species. J. Bacteriol 2005, 187, 7292–7308. [Google Scholar]
- Cell surface flocculin, Available online: http://www.uniprot.org/uniprot/E9P8M0 accessed on 5 April 2012.
- Lo, W.S.; Dranginis, A.M. The cell surface flocculin Flo11 is required for pseudohyphae formation and invasion by Saccharomyces cerevisiae. Mol. Biol. Cell 1998, 9, 161–171. [Google Scholar]
- Karunanithi, S.; Vadaie, N.; Chavel, C.A.; Birkaya, B.; Joshi, J.; Grell, L.; Cullen, P.J. Shedding of the mucin-like flocculin Flo11p reveals a new aspect of fungal adhesion regulation. Curr. Biol 2010, 20, 1389–1395. [Google Scholar]
- Veelders, M.; Brückner, S.; Ott, D.; Unverzagt, C.; Mösch, H.U.; Essen, L.O. Structural basis of flocculin-mediated social behavior in yeast. Proc. Natl. Acad. Sci. USA 2010, 107, 22511–22516. [Google Scholar]
- Muc1p. Available online: http://www.uniprot.org/uniprot/C8ZAR8 accessed on 6 April 2012.
- Lambrechts, M.G.; Bauer, F.F.; Marmur, J.; Pretorius, I.J. Muc1, a mucin-like protein that is regulated by Mss10, is critical for pseudohyphal differentiation in yeast. Proc. Natl. Acad. Sci. USA 1996, 93, 8419–8424. [Google Scholar]
- Secundino, N.; Kimblin, N.; Peters, N.C.; Lawyer, P.; Capul, A.A.; Beverley, S.M.; Turco, S.J.; Sacks, D. Proteophosphoglycan confers resistance of Leishmania major to midgut digestive enzymes induced by blood feeding in vector sand flies. Cell Microbiol 2010, 12, 906–918. [Google Scholar]
- Aebischer, T.; Harbecke, D.; Ilg, T. Proteophosphoglycan, a major secreted product of intracellular Leishmania mexicana amastigotes, is a poor b-cell antigen and does not elicit a specific conventional CD4+ T-cell response. Infect. Immun 1999, 67, 5379–5385. [Google Scholar]
- Marchler-Bauer, A.; Shennan, L.; Anderson, J.B.; Chitsaz, F.; Derbyshire, M.K.; DeWeese-Scott, C.; Fong, J.H.; Geer, L.Y.; Geer, R.C.; Gonzales, N.R.; et al. CDD: A conserved domain database for the functional annotation of proteins. Nucleic Acid Res 2011, 39, 225–229. [Google Scholar]
- Hsieh, W.C.; Chang, Y.; Hsu, M.C.; Lan, B.S.; Hsiao, G.C.; Chuang, H.C.; Su, I.J. Emergence of anti-red blood cell antibodies triggers red cell phagocytosis by activated macrophages in a rabbit model of Epstein-Barr virus-associated hemophagocytic syndrome. Am. J. Pathol 2007, 170, 1629–1639. [Google Scholar]
- Bairey, O.; Blickstein, D.; Stark, P.; Prokocimer, M.; Nativ, H.M.; Kirgner, I.; Shaklai, M. Serum CA 125 as a prognostic factor in non-Hodgkin’s lymphoma. Leuk. Lymphoma 2003, 44, 1733–1738. [Google Scholar]
- Yin, B.W.; Dnistrian, A.; Lloyd, K.O. Ovarian cancer antigen CA125 is encoded by the MUC16 mucin gene. Int. J. Cancer 2002, 98, 737–740. [Google Scholar]
- Albert, L.J.; Inman, R.D. Molecular mimicry and autoimmunity. N. Engl. J. Med 1999, 341, 2068–2074. [Google Scholar]
- Rose, N.R.; Mackay, I.R. Molecular mimicry: A critical look at exemplary instances in human diseases. Cell Mol. Life Sci 2000, 57, 542–551. [Google Scholar]
- Welsh, R.M.; Fujinami, R.S. Pathogenic epitopes, heterologous immunity and vaccine design. Nat. Rev. Microbiol 2007, 5, 555–563. [Google Scholar]
- Schneider, J.; Moragues, D.; MartÃnez, N.; Romero, H.; Jimenez, E.; Pontin, J. Cross-Reactivity between Candida albicans and human ovarian carcinoma as revealed by monoclonal antibodies PA10F and C6. Br. J. Cancer 1998, 77, 1015–1020. [Google Scholar]
- Krause, I.; Blank, M.; Cervera, R.; Font, J.; Matthias, T.; Pfeiffer, S.; Wies, I.; Fraser, A.; Shoenfeld, Y. Cross-Reactive epitopes on beta2-glycoprotein-I and Saccharomyces cerevisiae in patients with the antiphospholipid syndrome. Ann. N. Y. Acad. Sci 2007, 1108, 481–488. [Google Scholar]
- Oshitani, N.; Hato, F.; Suzuki, K.; Sawa, Y.; Matsumoto, T.; Maeda, K.; Higuchi, K.; Kitagawa, S.; Arakawa, T. Cross-Reactivity of yeast antigens in human colon and peripheral leukocytes. J. Pathol 2003, 199, 361–367. [Google Scholar]
- Srinivasappa, J.; Saegusa, J.; Prabhakar, B.S.; Gentry, M.K.; Buchmeier, M.J.; Wiktor, T.J.; Koprowski, H.; Oldstone, M.B.; Notkins, A.L. Molecular mimicry: Frequency of reactivity of monoclonal antiviral antibodies with normal tissues. J. Virol 1986, 57, 397–401. [Google Scholar]
- Punta, M.; Ofran, Y. The rough guide to in silico function prediction, or how to use sequence and structure information to predict protein function. PLoS Comput. Biol 2008, 4, e1000160. [Google Scholar]
- Sleator, R.D.; Walsh, P. An overview of in silico protein function prediction. Arch. Microbiol 2010, 192, 151–155. [Google Scholar]
- Glucan 1,4-alpha-glucosidase activity, Available online: http://amigo.geneontology.org/cgi-bin/amigo/term-details.cgi?term=GO:0004339 accessed on 9 April 2012.
- GO:0008061 chitin binding, Available online: http://www.ebi.ac.uk/QuickGO/GTerm?id=GO:0008061 accessed on 9 April 2012.
- Cation transport, Available online: http://amigo.geneontology.org/cgi-bin/amigo/term-details.cgi?term=GO:0006812 accessed on 9 April 2012.
- ATP synthesis coupled proton transport, Available online: http://amigo.geneontology.org/cgi-bin/amigo/term-details.cgi?term=GO:0015986 accessed on 9 April 2012.
- Seelenmeyer, C.; Wegehingel, S.; Lechner, J.; Nickel, W. The cancer antigen CA125 represents a novel counter receptor for galectin-1. J. Cell Sci 2003, 116, 1305–1318. [Google Scholar]
- Rump, A.; Morikawa, Y.; Tanaka, M.; Minam, S.; Umesaki, N.; Takeuchi, M.; Miyajima, A. Binding of ovarian cancer antigen CA125/MUC16 to mesothelin mediates cell adhesion. J. Biol. Chem 2004, 279, 9190–9198. [Google Scholar]
- Patankar, M.S.; Jing, Y.; Morrison, J.C.; Belisle, J.A.; Lattanzio, F.A.; Deng, Y.; Wong, N.K.; Morris, H.R.; Dell, A.; Clark, G.F. Potent suppression of natural killer cell response mediated by the ovarian tumor marker. Gynecol. Oncol 2005, 99, 704–713. [Google Scholar]
- Gipson, I.K.; Blalok, T.; Tisdale, A.; Spurr-Michaud, S.; Allcorn, S.; Stavreus-Evers, A.; Gemzell, K. Muc16 is lost from the uterodome (pinopode) surface of the receptive human endometrium: In vitro evidence that MUC16 is a barrier to trophoblast adherence. Biol. Reprod 2008, 78, 134–142. [Google Scholar]
- Özkucur, N.; Perike, S.; Sharma, P.; Funk, R.H.W. Persistent directional cell migration requires ion transport proteins as direction sensors and membrane potential differences in order to maintain directedness. BMC Cell Biol 2011, 12. [Google Scholar] [CrossRef]
- Gloor, S.; Antonicek, H.; Sweadner, K.J.; Pagliusi, S.; Frank, R.; Moos, M.; Schachner, M. The adhesion molecule on glia (AMOG) is a homologue of the beta subunit of the Na,K-ATPase. J. Cell Biol 1990, 110, 165–174. [Google Scholar]
- Straver, M.H.; Smit, G.; Kijne, J.W. Purification and partial characterization of a flocculin from brewer’s yeast. Appl. Environ. Microbiol 1994, 60, 2754–2758. [Google Scholar]
- Adams, J.C. Cell-Matrix contact structures. Cell Mol. Life Sci 2001, 58, 371–392. [Google Scholar]
- Duraisamy, S.; Ramasamy, S.; Kharbanda, S.; Kufe, D. Distinct evolution of the human carcinoma-associated transmembrane mucins, MUC1, MUC4 and MUC16. Gene 2006, 373, 28–34. [Google Scholar]
- UniProtKB. Available online: http://www.uniprot.org/ accessed on 2 April 2012.
- National Center for Biotechnology Information. Available online: http://www.ncbi.nlm.nih.gov accessed on 30 March 2012.
- The UniProt Consortium (UniProt). Reorganizing the protein space at the Universal Protein Resource (UniProt). Nucleic Acids Res. 2012, 40, D71–D75.
- Altschul, S.; Gish, W.; Miller, W.; Myers, E.; Lipman, D. Basic local alignment search tool. J. Mol. Biol 1990, 215, 403–410. [Google Scholar]
- Mountm, D.W. Using the Basic amd Local Alignment Search Tool (BLAST). In Cold Spring Harbor Protocols; Cold Spring Harbor Laboratory Press: Cold Spring Harbor, NY, USA, 2007; Volume 14, p. 17. [Google Scholar]
- Friedberg, I.; Harder, T.; Godzik, A. JAFA: A protein function annotation meta-server. Nucleic Acids Res 2006, 34, W379–W381. [Google Scholar]
- Joined Assembly of Function Annotations-JAFA. Available online: http://jafa.burnham.org/ accessed on 6 December 2006.
- Hawkins, T.; Luban, S.; Kihara, D. Enhanced automated function prediction using distantly related sequences and contextual association by PFP. Protein Sci 2006, 15, 1550–1556. [Google Scholar]
- Kihara Bioinformatics Laboratory. Available online: http://dragon.bio.purdue.edu/pfp accessed on 21 August 2008.
- Juhl Jensen, L.; Stærfeldt, H.H.; Brunak, S. Prediction of human protein function according to Gene Ontology categories. Bioinformatics 2003, 19, 635–642. [Google Scholar]
- GO Annotation Tools. Available online: http://www.geneontology.org/GO.tools.annotation.shtml accessed on 21 February 2012.
- Tatebayashi, K.; Tanaka, K.; Yang, H.Y.; Yamamoto, K.; Matsushita, Y.; Tomida, T.; Imai, M.; Saito, H. Transmembrane mucins Hkr1 and Msb2 are putative osmosensors in the SHO1 branch of yeast HOG pathway. EMBO J 2007, 26, 3521–3533. [Google Scholar]
- Pelaseyed, T.; Hansson, G.C. CFTR anion channel modulates expression of human transmembrane mucin MUC3 through the PDZ protein GOPC. J. Cell Sci 2011, 124, 3074–3083. [Google Scholar]
- Cullen, P.J.; Spraguem, G.F. The roles of bud-site-selection proteins during haploid invasive growth in yeast. Mol. Biol. Cell 2002, 13, 2990–3004. [Google Scholar]
- Bozzuto, G.; Ruggieri, P.; Molinari, A. Molecular aspects of tumor cell migration and invasion. Ann. Ist. Super. Sanita 2010, 46, 66–80. [Google Scholar]
|Table 1. Sequence similarity search for Q8WXI7 (MUC16/CA125) entry.|
|Database||Hit *||Protein/Conserved Domain **||Organism||Length||Identity||Score||E-value|
|Virus||O39781/Q6SV6WO||MembraneGlycoprotein, gp2/Gp2 **||Equine herpesvirus 1||806||25%||295||1 × 10−23|
|E2GKY4||Glycoproteingp350-220/BLLF1 **||Epstein Barr virus||877||26%||170||3 × 10−9|
|Bacteria||B2ISC7/Q97P71||Cell surface anchor family protein||Streptococcus pneumoniae(strain GSP14)||4695||17%||669||4 × 10−66|
|Q4L9PO||Serine-rich adhesion for platelets||Staphylococcus haemolyticus (strain JCSC1435)||3608||20%||625||5 × 10−61|
|Fungi||E9P8M0||Cell surface flocculin||Saccharomyces cerevisiae||1630||24%||499||4 × 10−47|
|C8ZAR8||Muc1p||Saccharomyces cerevisiae||1576||23%||429||6 × 10−39|
|Eukaryota||E9AEM9||Proteophosphoglycan 5||Leishmania major||17392||18%||1003||6 × 10−105|
E-value: <1 × 10−50—homology; 0.01–1 × 10−50—may be homology; 0.01–10 not significant, distant homology; >10—random;*searched by BLAST;**search by CDD v2.26-38392 PSSMs.
|Table 2. Predicted gene ontology (GO) categories for Q8WXI7 (MUC16/CA125) entry *.|
|Biological process||Molecular function||Cellular component|
|0006812||5363||Cation transport||0005515||3567||Protein binding||0005624||2,4775||Membrane|
|0007155||4679||Cell adhesion||0004867||3371||Endopeptidase inhibitor activity||0005887||4,420||Integral to plasma membrane|
|0006929||3310||Substrate-bound cell migration||0004672||2914||Protein kinase activity||0005622||3,129||Intracellular|
|0050652||2664||Polysachharide biosynthesis||0004674||2623||Ser/Thr kinase activity||0016021||2,363||Integral to membrane|
|0007166||2554||Cell surface receptor linked signal transduction||0005529||2445||Sugar binding||0005578||2,118||Extracellular matrix (sensu Metazoa)|
|0007165||2416||Signal transduction||0005524||2219||ATP binding||0005634||1,939||Nucleus|
|0006917||2213||Induction of apoptosis||0008270||2206||Zinc ion binding||0005856||1,764||Cytoskeleton|
|0008228||2079||Opsonization||0003804||2154||Coagulation factor Xa activity||0009897||1,633||External side of plasma membrane|
|0035162||2071||Embryonic hemopoiesis||0046703||2075||NK cell like-receptor binding||0005615||1,531||Extracellular space|
*searched by http://dragon.bio.purdue.edu/pfp; selected results.
|Biological process||Molecular function||Cellular component|
|0015986/6||2.00||ATP synthesis coupled proton transport||0004339/6||2.00||Glucan 1,4-alpha glucosidase activity||0005886/3||1.00||Plasma membrane|
|0006030/6||2.00||Chitin metabolism||0005524/5||1.67||ATP binding||0016469/2||0.67||Proton-transporting two-sector ATPase complex|
|0000272/6||2.00||Polysaccharide catabolism||0008061/4||1.33||Chitin binding||0005615/2||0.67||Extracellular space|
|0007160/4||1.33||Cell matrix adhesion||0005515/2||0.67||Protein binding||-||-||-|
|0007124/3||1.00||Pseudohyphal growth||0005554/1||0.33||Molecular function unknown||-||-||-|
|0001403/3||1.00||Invasive growth (sensu Saccharomyces)||-||-||-||-||-||-|
*searched by http://jafa.burnham.org; selected results.
© 2012 by the authors; licensee Molecular Diversity Preservation International, Basel, Switzerland. This article is an open-access article distributed under the terms and conditions of the Creative Commons Attribution license (http://creativecommons.org/licenses/by/3.0/).