Herpes simplex virus glycoprotein g enhances chemotaxis and axonal growth through modification of plasma membrane microdomains and receptor trafficking

Resumen

Herpes simplex virus type 1 and 2 (HSV-1 and HSV-2) are two highly prevalent, neurotrophic human pathogens. The interplay between HSV and the immune system is important to determine the onset and the outcome of the viral infection, but yet, the precise modulation of the immune system by HSV remains poorly understood. We have previously identi"ed secreted HSV glycoprotein G (SgG) as the "rst viral chemokine binding protein (vCKBP) that, in sharp contrast to all vCKBPs described to date, enhances chemokine function both in vitro and in vivo. Furthermore, we have recently shown the ability of SgG to interact with and modulate the function of neutrophins such as nerve growth factor (NGF), essential elements of the biology of the nervous system. HSV gG interaction with chemokines induces an enhanced chemotaxis mediated by an augmented receptor signalling and directionality of cell movement. Surface plasmon resonance (SPR) and cell binding assays show that SgG binds to the cell surface through the interaction with glycosaminoglycans. We demonstrate that SgG modulates membrane tra!cking, delays chemokine-mediated internalization, and leads to an increase in the level of chemokine receptors at the cell surface. Moreover, SgG-induced impact on the architecture of the plasma membrane microdomains promotes the incorporation of CXCR4 into lipid rafts and di%erentially alters the fate of other receptors. The link between the aggregation state of chemokine receptors and their functionality has not been characterized. Here, we provide evidences showing that the enhancement of chemokine function is associated with an SgGinduced increase in the presence of CXCR4 small oligomers on the surface, accompanied by conformational rearrangements in CXCR4 homodimers. SPR-based assays were set up in order to characterize the ability of HSV viral particles to interact with chemokines. Our results demonstrate that HSV virions bind chemokines. The functionality of the virus-chemokine interaction was analyzed in vitro. We show that HSV particles are chemotactic in transwell assays and that they synergize with chemokines to enhance migration. Importantly, we found that envelope-anchored gG has an important contribution to these activities, suggesting the relevance of the HSV gG-chemokine interaction during early stages of the viral infection.