X4‐tropic human immunodeficiency virus IIIB utilizes CXCR4 as coreceptor, as distinct from R5X4‐tropic viruses

Abstract

Human immunodeficiency viruses initiate infections via CCR5 coreceptors and then change their tropism to C-X-C chemokine receptor type 4 (CXCR4), this change being associated with rapid disease progression. HIV-1IIIB, a widely described pure X4-tropic strain, is distinct from R5X4-tropic viruses. In this study, the requirement for amino terminal regions (NTRs) of CXCR4 for entry of HIV-1IIIB virus into host cells was examined and compared to that of R5X4-tropic viruses. CXCR4 and its deletion mutant (CXCR4DNTR23; first 23 amino acids removed from NTR) were amplified to examine their coreceptor activities. NP-2/CD4/CXCR4 and NP-2/CD4/CXCR4DNTR23 cell lines were prepared accordingly. Indirect immune fluorescence assay (IFA), PCR, and reverse transcriptase (RT) activity were used to compare the process of infection of host cells by HIV-1IIIB virus, one R5-tropic and five other R5X4-tropic viruses. All the R5X4-tropic HIVs were found to utilize both CCR5 and CXCR4 but unable to use CXCR4DNTR23 as coreceptors. In contrast, X4-tropic HIV-1IIIB was found to preferentially infect through CXCR4DNTR23. Viral antigens in infected NP-2/CD4/CXCR4DNTR23 cells were detected by IFA and confirmed by detection of proviral DNA and by performing RTassays on the spent cell-supernatants. In dual tropic viruses, deletion of 23 amino acids from NTR abrogates the coreceptor activity of CXCR4. This observation demonstrates that NTR of CXCR4 have an obligatory coreceptor role for dual tropic viruses. However, HIV-1IIIB may have different requirements for NTR than R5X4 viruses or may infect host cells independent of NTR of CXCR4.Key words coreceptor, C-X-C chemokine receptor type 4, deletion mutant, X4/R5X4-tropic HIV.Human immunodeficiency viruses infect and enter into host cells by binding their mature envelop (env) glycoprotein, gp120, to CD4 as primary receptor (1, 2) and to chemokine receptors, CCR5, and CXCR4, exclusively or mutually, as major coreceptors (3, 4). List of Abbreviations: 7TM, seven-transmembrane receptor; CCR5, C-C chemokine receptor type 5; CD, cluster of differentiation; CKR, chemokine receptor; CXCR4, C-X-C chemokine receptor type 4; CXCR4DNTR23, mutant of CXCR4 made by removal of first 23 amino acids from NTR; DMEM, Dulbecco's modified EMEM; EMEM, Eagle's minimum essential medium; GAPDH, glyceraldehyde-3-phosphate dehydrogenase; GPCR, G proteincoupled receptor; IFA, immune fluorescence assay; NCBI,

HIV gp120 upregulates tonic inhibition through α5-containing GABAARs

“…Viral tropism is determined by gp120 binding to CD4 and a chemokine co-receptor. The IIIB strain of gp120 used in this study binds to CXCR4 (Islam et al, 2013;Moore et al, 1997), consistent with inhibition of gp120-evoked effects by a CXCR4 receptor antagonist. Recombinant gp120 IIIB has previously been shown to induce release of inflammatory cytokines, including IL-1β, from human monocytes (Clouse et al, 1991).…”

“…Twoway ANOVAs were followed by Tukey's post hoc test, *p<0.05, ** p<0.01, *** p<.001 Inhibition of CXCR4 with AMD3100 prevents gp120-induced changes in GABA A R signaling. Because gp120 IIIB binds to CXCR4 (Islam et al, 2013;Moore et al, 1997) we propose that the signaling cascade starts with this receptor. While multiple cell types including neurons, astrocytes, and microglia express CXCR4, LME treatment to remove microglia prevented gp120-induced changes in GABA A R signaling in neurons.…”

CKR-L3, a deletion version CCR6-isoform shows coreceptor-activity for limited human and simian immunodeficiency viruses

“…On the other hand, among the deleted portion of CKR-L3, there was no tyrosine residues, which were reported to be part of the NTR of CCR5 considered vital for viral entry [43]. Potential functional roles of tyrosines in the CXCR4-NTR has been described in our previous reports, where we showed a partial deletion of CXCR4-NTR containing tyrosines abolishes its coreceptor function for many dual tropic HIV and SIV viruses [44]. Therefore, the natural deletion of a small NTR-part without tyrosine from CCR6 does not exert a deleterious coreceptor-function, rather promotes CKR-L3.…”

HIV gp120‐induced neuroinflammation potentiates NMDA receptors to overcome basal suppression of inhibitory synapses by p38 MAPK

“…; Islam et al . ). Recombinant gp120 IIIB has previously been demonstrated to induce release of inflammatory cytokines including IL‐1β from human monocytes (Clouse et al .…”