The B-Oligomer of Pertussis Toxin Deactivates Cc Chemokine Receptor 5 and Blocks Entry of M-Tropic HIV-1 Strains

Abstract

Infection of target cells by HIV-1 requires initial binding interactions between the viral envelope glycoprotein gp120, the cell surface protein CD4, and one of the members of the seven-transmembrane G protein–coupled chemokine receptor family. Most primary isolates (R5 strains) use chemokine receptor CCR5, but some primary syncytium-inducing, as well as T cell line–adapted, strains (X4 strains) use the CXCR4 receptor. Signaling from both CCR5 and CXCR4 is mediated by pertussis toxin (PTX)-sensitive Gi proteins and is not required for HIV-1 entry. Here, we show that the PTX holotoxin as well as its binding subunit, B-oligomer, which lacks Gi-inhibitory activity, blocked entry of R5 but not X4 strains into primary T lymphocytes. Interestingly, B-oligomer inhibited virus production by peripheral blood mononuclear cell cultures infected with either R5 or X4 strains, indicating that it can affect HIV-1 replication at both entry and post-entry levels. T cells treated with B-oligomer did not initiate signal transduction in response to macrophage inflammatory protein (MIP)-1β or RANTES (regulated upon activation, normal T cell expressed and secreted); however, cell surface expression of CCR5 and binding of MIP-1β or HIV-1 to such cells were not impaired. The inhibitory effect of B-oligomer on signaling from CCR5 and on entry of R5 HIV-1 strains was reversed by protein kinase C (PKC) inhibitors, indicating that B-oligomer activity is mediated by signaling events that involve PKC. B-oligomer also blocked cocapping of CCR5 and CD4 induced by R5 HIV-1 in primary T cells, but did not affect cocapping of CXCR4 and CD4 after inoculation of the cultures with X4 HIV-1. These results suggest that the B-oligomer of PTX cross-deactivates CCR5 to impair its function as a coreceptor for HIV-1.

Inhibition of intra‐ and extra‐cellular Tat function and HIV expression by pertussis toxin B‐oligomer

“…On the other hand, it is known that PTX-B possesses several anti-HIV mechanisms. It interferes with entry of R5-dependent HIV-1 by uncoupling R5 from CD4 [20]. Also, it interferes with post-entry events in the HIV life cycle [20,22].…”

“…It interferes with entry of R5-dependent HIV-1 by uncoupling R5 from CD4 [20]. Also, it interferes with post-entry events in the HIV life cycle [20,22]. In this regard, its anti-HIV effect has been linked to inhibition of NF-kB activation [23].…”

“…PTX-B inhibits entry of R5-dependent HIV-1 in T cells and macrophages and post-entry steps of both R5-and X4-dependent HIV-1 life cycle in primary T cells [20,21], monocyte-derived macrophages (MDM) [22], as well as viral expression in chronically infected MDM [21,22] and cytokine-stimulated U1 cells [22,23]. PTX-B also inhibits Tat-driven transactivation in T lymphoid Jurkat cells [21], and stimulates anti-HIV specific cytotoxic T lymphocyte responses [24].…”

Use of G-Protein-Coupled and -Uncoupled CCR5 Receptors by CCR5 Inhibitor-Resistant and -Sensitive Human Immunodeficiency Virus Type 1 Variants

“…PTX consists of two subunits: an enzymatically active A protomer that ribosylates the G␣ i subunit and prevents it from coupling to the cognate GPCR and a binding (B) oligomer that mediates the toxin's biological effects independently of G␣ i ( Fig. 2A) (37,38). To determine whether the effect of PTX on VVC activity is mediated by G␣ i uncoupling, we performed an experiment similar to that described for Fig.…”

Pertussis Toxin B-Oligomer Suppresses IL-6 Induced HIV-1 and Chemokine Expression in Chronically Infected U1 Cells via Inhibition of Activator Protein 1

“…macrophages (MDM) (3,8,9). In addition, PTX-B inhibited the replication of both R5 and X4 HIV-1 strains by acting at one or more postentry mechanisms in activated primary T cells, MDM (3,10), and chronically infected cell lines, such as the promonocytic U1 cell line stimulated with PMA or cytokines (9,11).…”