Sergey Iordanskiy, Ph.D.
Research Interests The field of my research interests is HIV molecular biology and pathogenesis. Currently I am focusing on two general problems: i) virus-cell interaction at early stages of HIV replication and ii) HIV-1 variability and acquisition of drug resistance - interaction of drug-resistant mutants with a host cell. 1.The early phase of HIV life cycle (includes virus entering into the target cell, reverse transcription, delivery of intact DNA to the site of integration and integration itself) occurs in the presence of an active counteraction of the target cell. During the evolution, retroviruses acquired specific mechanisms that allow them protect their genome and reverse transcription machinery and perform transportation of the viral genetic material towards the site of integration. From this standpoint, formation of multimolecular complexes termed reverse transcription complexes (RTCs) at a post-entry step of infection may be considered as one of key adaptations of retroviruses that accomplishes protective and transport functions. Meanwhile, since relatively few virus particles initiate infection under natural conditions, the early phase of retroviral life cycle is particularly vulnerable to host anti-viral responses. Thus, analysis of virus-cell (RTC-cell) interaction at this stage of the viral replication cycle may contribute to identify potential targets for medical intervention aimed at activation of the cellular defense mechanisms. In context of this problem, we focused on the analysis of intracellular trafficking of HIV-1 RTCs and effect of host cell proteins on RTC formation, maturation and transport. We found that successful integration of viral cDNA into the chromatin requires completion of reverse transcription and rearrangement of the protein composition of RTCs in the cytoplasm before import into the nucleus through the nuclear pore complex (NPC) (Iordanskiy et al, 2006; Iordanskiy and Bukrinsky, 2007). Change of the protein composition is likely required for surface exposure of the proteins comprising nuclear localization signal (NLS) and removal of viral proteins, which can block NLSs of the RTC karyophilic components. Many host cellular proteins are involved in interaction with HIV-1 RTCs. We found that host heat-shock proteins are active players of intracytoplasmic trafficking and nuclear import or RTCs. Chaperones of the Hsp70 family facilitate access of the viral cores to the cellular interior and RTC formation by means of suppression of the ubiquitination of RTC proteins and their proteasomal degradation. On the other hand, at later stages of HIV replication in non-dividing cells (primary macrophages), Hsp70 inhibits infection by suppressing the nuclear import of the HIV-1 RTCs, probably through interfering with nuclear transport mediated by HIV-1 protein Vpr (Iordanskiy et al., 2004). Thus, implication of the host cell chaperones from Hsp 70 family in multiply molecular pathways associated with HIV-1 life cycle progression suggests that heat-shock proteins, in combination with other cellular factors, can modulate host-cellular antiviral machinery and be involved in intrinsic immunity response. Now we use this approach to analysis of virus-cell interaction for investigation of a host cellular effect on replication of drug-resistant HIV mutants. 2. HIV-1 is classified into three distinct groups: M (major), O (outlier) and N (non M/non O). The group M is composed of 11 subtypes or clades named A through K, which circulate in populations around the globe. More then 55% of HIV patients are infected with subtype C. This clade of HIV-1 is most rapidly expanding now in South-Eastern Asia and Sub-Saharan regions of Africa. This phenomenon can be explained by higher potential for transmission, especially heterosexual transmission of subtype C in compare with other group M clades. On the other hand, replicative capacity of HIV-1 C in competition assays are significantly less than other group M clades. Data for drug resistance acquisition, which are important for evaluation of an evolution potential of a virus in the chemotherapy era, are also contradictory. For instance, subtype C demonstrates higher frequency of nevirapine-resistant mutations after single dose of this non-nucleoside reverse transcriptase inhibitor (NNRTI) than subtypes A and D; on the other hand, subtype C yields to subtype B in acquisition of mutations of resistance to protease and nucleoside reverse transcriptase inhibitors (NRTI). Mutations of resistance to reverse transcriptase inhibitors reduce drug susceptibility and decrease replicative capacity of a virus (low-fit mutants). NRTI and NNRTI-resistance mutations reside primarily in the subdomains of reverse transcriptase, which are responsible for the geometry of catalytic sites of the enzyme. They decrease efficiency of reverse transcription and result in delayed and inaccurate RT reaction. Therefore, RTCs of drug-resistant RT mutants persist in the cytoplasm of an infected cell for a long time and they may be more effectively destroyed by cellular defense mechanisms than RTCs of HIV-1 wild type. Thus, in the context of this hypothesis we are focusing on the following questions: (i) are there differences in drug resistance acquisition between C and other subtypes of HIV-1; (ii) are there differences in replicative capacities between drug resistant mutants of subtype C and other subtypes; (iii) how do low-fit drug-resistant mutants interact with host cells, are there cellular mechanisms to eliminate infection of HIV-1 drug-resistant strains? Currently we are working on generation of chimeric viruses between the subtypes B and C HIV-1 and laboratory model for quantitative analysis of selection and determination of drug resistant mutations and examination of host-cellular effect on replication of these mutants. Research Articles Iordanskiy S., Berro R., Altieri M., Kashanchi F. and Bukrinsky M. Intracytoplasmic maturation of the human immunodeficiency virus type 1 reverse transcription complexes determines their capacity to integrate into chromatin. Retrovirology 2006. 3: 4. Iordanskiy S., Zhao Y., DiMarzio P., Agostini I., Dubrovsky L., and Bukrinsky M. Heat-shock protein 70 exerts opposing effects on Vpr-dependent and Vpr-independent HIV-1 replication in macrophages. Blood. 2004. 104: 1867-1872. Iordanskiy S., Zhao Y., Dubrovsky L., Iordanskaya T., Chen M, Liang D., and Bukrinsky M. Heat-shock protein 70 protects cells from cell cycle arrest and apoptosis induced by human immunodeficiency virus type 1 viral protein R. 2004. J.Virol. 2004. 78: 9697-9704. Iordanskiy S., Iordanskaya T., Quivy V., Van Lint C. and Bukrinsky M. The B-oligomer of pertussis toxin inhibits HIV-1 LTR-driven transcription through suppression of the NF-kB p65 subunit activity. Virology. 2002. 302: 195-206.
Invited Reviews and Chapters Iorsanskiy S. and Bukrinsky M. Analysis of viral and cellular proteins in HIV-1 reverse transcription complexes by co-immunoprecipitation. In: HIV Protocols, Second edition, Series ‘Methods in Molecular Medicine’, Humana Press [in press; scheduled for the beginning 2008]. Iordanskiy S. and Bukrinsky M. Reverse transcription complex: the key player of the early phase of HIV replication. Future Virology. 2007. 2(1): 49-64. Iordanskiy, S, Morrow, MP, Bukrinsky, M, Bushman, FD. Early Phase of HIV Life Cycle. In: Reactome: HIV Infection: HIV Life Cycle. Cold Spring Harbor Laboratory, 2006-05-16. |
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