Interaction between the Cytoplasmic Domain of ICAM-1 and Pr55 ^Gag Leads to Acquisition of Host ICAM-1 by Human Immunodeficiency Virus Type 1

Abstract

We have examined the molecular basis for the selective incorporation of the adhesion molecule ICAM-1 within human immunodeficiency virus type 1 (HIV-1). The process of ICAM-1 incorporation was investigated by using different ICAM-1 constructs in combination with virus capture and immunoprecipitation studies, Western blot and confocal microscopy analyses, and infectivity assays. Experiments conducted with viruses bearing a truncated version of ICAM-1 revealed that the cytoplasmic domain of ICAM-1 governs insertion of this adhesion molecule into HIV-1. Further experiments suggested that there is an association between ICAM-1 and the virus-encoded Pr55Gag polyprotein. This study represents the first demonstration that structural Gag polyproteins play a key role in the uptake of a host-derived cell surface by the virus entity. Taken together, our results indicate that interactions between viral and cellular proteins are responsible for the selective uptake of host ICAM-1 by HIV-1. This observation describes a new strategy by which HIV-1 can modulate its replicative cycle, considering that insertion of ICAM-1 within nascent virions has been shown to increase virus infectivity.

Basic Motifs Target PSGL-1, CD43, and CD44 to Plasma Membrane Sites Where HIV-1 Assembles

“…We speculate that these previous observations likely represent a passive mode of incorporation. Alternatively, in the overexpression context used in these studies, a small population of ICAM-1 molecules may escape from a binding partner that would prevent specific recruitment to assembly sites and, as a result, engage in direct or indirect interactions with Gag (85). Consistent with these interpretations, a previous study showed that the amounts of ICAM-1 present on the virions correlate with the levels of ICAM-1 expression on virus-producing 293T cells (86).…”

Selective Acquisition of Host-Derived ICAM-1 by HIV-1 Is a Matrix-Dependent Process

“…Gag precursor polyprotein, which codes for all the structural proteins of HIV-1 (20,(38)(39)(40)(41), acts as a dominant actor in the process of acquisition of ICAM-1 (30). Therefore, our initial series of investigations were aimed at corroborating this observation using a simple and pertinent model of VLPs mimicking the immature virion state.…”

“…The presence of host-derived ICAM-1 within VLPs and NL4.3-derived virus (both WT and mutated forms) was monitored by capturing viruses with immunomagnetic beads using a previously reported procedure, with slight modifications (30). In brief, streptavidin-coated magnetic beads (7.5 ϫ 10 5 beads) (Dynabeads M280; Invitrogen, Burlington, Canada) were washed once with PBS supplemented with 5% bovine serum albumin (BSA) (binding medium) using a vertical magnetic plate.…”

“…At 6 h posttransfection, the medium was discarded, cells were washed two times with phosphate-buffered saline (PBS), and 10 ml of fresh medium was added. Immature HIV-1 particles were produced by treating the virus producer cell lines with indinavir (20 M) during transfection experiments (30). PBMCs from healthy donors were isolated by Ficoll-Hypaque density gradient centrifugation and cultured in the presence of the mitogenic agent phytohemagglutinin P (PHA-P; Sigma, St. Louis, MO, USA) (3 g/ml) and recombinant human interleukin-2 (30 units/ml) for 3 days at 37°C under a 5% CO 2 atmosphere prior to virus infection.…”

Plunder and Stowaways: Incorporation of Cellular Proteins by Enveloped Viruses

“…Given that the connection between ICAM-1 and the cortical actin was demonstrated on one hand and that the interaction between HIV-1 Gag and filamentous actin was confirmed on the other hand, it was proposed that the insertion of Gag, actin, and ICAM-1 within nascent virions would be in the form of a multimolecular complex (9).…”