A Comprehensive Analysis of Human Endogenous Retroviruses HERV-K (HML.2) from Teratocarcinoma Cell Lines and Detection of Viral Cargo in Microvesicles
Abstract
:1. Introduction
2. Results
2.1. Proteins and Parameters of HML.2 from Teratocarcinoma Cell Lines GH and Tera-1
2.2. Reverse Transcriptase (RT) Activity in HML.2 GH and Tera-1
2.3. Deglycosylation of HML.2 GH and HML.2 Tera-1
2.4. Analyses of Viral Particles and Extracellular Vesicles by Negative Staining and Ultrathin Section TEM
- Group 1—Bald particles with amorphous capsids (Figure 3(b1)). About 60–70%.
- Group 2—Bald particles with fragmented capsids (Figure 3(b2)). Not frequent.
- Group 4—Particles with 6–8 nm long SP and condensed or partially condensed capsids about 65–80 nm in diameter (Figure 3(b4,b5) left). Such particles were not frequent (~1%). Several virions with partially condensed capsids and small surface protrusions (~2–3 nm) located at nearly equal distance between each other were detected. These protrusions are likely representing the TM stumps (Figure 3(b5) right).
- Group 5—Extracellular vesicles with captured “viral elements” displayed a variety of vesicular assemblies containing HML.2 GH budding structures with and without SP (Figure 3(c1–c9)). Association of HML.2 Tera-1 with MVs was exceptionally rare.
2.5. Search for Virus Diversification in HML.2 Pool and Analyses of SU and vRNA in Fractions of the Sucrose Density Gradient
2.6. Viral RNA Packaged in HML.2 GH and HML.2 Tera-1, Analyses of env Type 2 Gene
2.7. Quantification of HML.2 Particles Released from GH and Tera-1 Cells
3. Discussion
4. Materials and Methods
4.1. Cells and Cellular Lysates
4.2. Antibodies
4.3. Virus Isolation, Sucrose Density Gradient Centrifugation (Dgc)
4.4. Transfection of Cells and Purification of Recombinant HML.2 Particles
4.5. Western Blotting and Dot Blot
4.6. PNGase F Treatment
4.7. RNA Extraction, RT-PCR and RT-qPCR
4.8. Reverse Transcriptase Assay
4.9. Cloning and Sequence Analysis
4.10. Transmission Electron Microscopy (TEM)
4.11. Software
4.12. Sequences Deposited to the GenBank
5. Summary and Conclusions
- -
- As a consequence of active expression of several proviruses, GH cells produced 4–5 times more viruses, compared to Tera-1 cells. It is likely that SU and TM of HML.2 are completely glycosylated. Truncated TM variant (p24-TM), a low SU content and reduced RT activity were disclosed in examined HML.2.
- -
- Bald virions with amorphous capsids were the most common morphological variants in HML.2 pools. Virus particles with SP and condensed (collapsed) capsids were rarely detected.
- -
- GH cells actively release MVs. During budding, MVs can capture fragments of plasma membrane with HML.2 elements at different stages of assembly. Judging from the TEM images, maturation of virus particles inside MVs may take place. The release of MVs from Tera-1 cells was insignificant.
- -
- We assume that MVs with HML.2 elements upon delivery to target cells can trigger cell signaling systems, promote inflammation and autoimmune diseases.
- -
- Six different HML.2 transcripts including two recombinant variants were packaged into virus particles from GH cells. However, HML.2 Tera-1 contained only HERV-K108 env transcripts and similar sequences.
- -
- It was assessed that, in 24 h, one GH cell can produce ~27 virions, while Tera-1 cell ~6 virions, whereas human lymphocytes chronically infected with HIV-1 release about 1 × 104 virions.
Author Contributions
Funding
Institutional Review Board Statement
Informed Consent Statement
Data Availability Statement
Acknowledgments
Conflicts of Interest
References
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Viruses | Total gls | SU gls | TM gls | TM Ectodomain (a.a./gls) | TM Ectodomain IG (a.a./gls) |
---|---|---|---|---|---|
HERV-K108 (HML.2) | 11 | 7 * | 4 | 168/4 | 42 |
HERV-K109 (HML.2) | 11 | 7 * | 4 | 168/4 | 42 |
HERV-K113 (HML.2) | 11 | 7 * | 4 | 170/4 | ~42.5 |
HERV-K115 (HML.2) | 11 | 7 | 4 | 170/4 | ~42.5 |
HERV-K108 (HML.2) | 11 | 7 | 4 | 170/4 | ~42.5 |
JSRV | 9 | 6 | 3 | 171/3 | 57 |
ENTV | 8 | 5 | 3 | 170/3 | ~56.6 |
MMTV | 5 | 3 | 2 | 168/2 | 84 |
MPMV | 11 | 10 | 1 | 167/1 | 167 |
HIV-1 | 31 | 24 | 7 (-3) ** | 170/4 | ~42.5 |
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Morozov, V.A.; Morozov, A.V. A Comprehensive Analysis of Human Endogenous Retroviruses HERV-K (HML.2) from Teratocarcinoma Cell Lines and Detection of Viral Cargo in Microvesicles. Int. J. Mol. Sci. 2021, 22, 12398. https://doi.org/10.3390/ijms222212398
Morozov VA, Morozov AV. A Comprehensive Analysis of Human Endogenous Retroviruses HERV-K (HML.2) from Teratocarcinoma Cell Lines and Detection of Viral Cargo in Microvesicles. International Journal of Molecular Sciences. 2021; 22(22):12398. https://doi.org/10.3390/ijms222212398
Chicago/Turabian StyleMorozov, Vladimir A., and Alexey V. Morozov. 2021. "A Comprehensive Analysis of Human Endogenous Retroviruses HERV-K (HML.2) from Teratocarcinoma Cell Lines and Detection of Viral Cargo in Microvesicles" International Journal of Molecular Sciences 22, no. 22: 12398. https://doi.org/10.3390/ijms222212398