Occludin controls HIV transcription in brain pericytes via regulation of SIRT‐1 activation

Abstract

HIV invades the brain early after infection; however, its interactions with the cells of the blood-brain barrier (BBB) remain poorly understood. Our goal was to evaluate the role of occludin, one of the tight junction proteins that regulate BBB functions in HIV infection of BBB pericytes. We provide evidence that occludin levels largely control the metabolic responses of human pericytes to HIV. Occludin in BBB pericytes decreased by 10% during the first 48 h after HIV infection, correlating with increased nuclear translocation of the gene repressor C-terminal-binding protein (CtBP)-1 and NFkB-p65 activation. These changes were associated with decreased expression and activation of the class III histone deacetylase sirtuin (SIRT)-1. Occludin levels recovered 96 h after infection, restoring SIRT-1 and reducing HIV transcription to 20% of its highest values. We characterized occludin biochemically as a novel NADH oxidase that controls the expression and activation of SIRT-1. The inverse correlation between occludin and HIV transcription was then replicated in human primary macrophages and differentiated monocytic U937 cells, in which occludin silencing resulted in 75 and 250% increased viral transcription, respectively. Our work shows that occludin has previously unsuspected metabolic properties and is a target of HIV infection, opening the possibility of designing novel pharmacological approaches to control HIV transcription.-

Junctional proteins of the blood-brain barrier: New insights into function and dysfunction

“…However, intriguing new evidence showed that occludin could largely control metabolic responses of human pericytes infected with HIV-1. 134 Along with this data, is preliminary proteomic analysis of occludin and claudin-4 in epithelial cells, which showed a close association of these proteins with trafficking, signaling and endocytotic pathways. 135 Thus, the redistribution of junction proteins may not only affect barrier physical properties directly but it may further modulate ongoing signaling processes enhancing BBB dysfunction.…”

Occludin regulates glucose uptake and ATP production in pericytes by influencing AMP-activated protein kinase activity

“…We recently explored the relationship between occludin and metabolic alterations in pericytes following HIV infection and showed that occludin impairs viral proliferation. 25 This wide range of metabolic effects could be achieved if occludin was partnered with integrative metabolic players like AMPK and SIRT-1. Both influence gene expression, activation of transcription factors, glucose metabolism and cellular energetics, 28,59,60 and our current and previous 25 findings strongly indicate the existence of a metabolic regulatory triad: OCCLUDIN-AMPK-SIRT1 ( Figure 7).…”

“…25 This wide range of metabolic effects could be achieved if occludin was partnered with integrative metabolic players like AMPK and SIRT-1. Both influence gene expression, activation of transcription factors, glucose metabolism and cellular energetics, 28,59,60 and our current and previous 25 findings strongly indicate the existence of a metabolic regulatory triad: OCCLUDIN-AMPK-SIRT1 ( Figure 7). This triple partnership is exemplified by our findings showing that pericytes become sensitive to insulin and enhance their glucose uptake in an AMPK-dependent manner when occludin levels are elevated, which is consistent with the involvement of SIRT1 and AMPK in regulation of insulin sensitivity.…”

“…Immunoblotting and spectrally resolved in-cell ELISA (SPRICE) were performed as previously described. 25 For SPRICE, cells were cultured in 96-well plates, stained with DRAQ-5 (1:100, Cell Signaling Technology, USA) as recommended by the manufacturer, and fixed with ice-cold methanol. Non-specific binding sites were blocked with BlockAid (Invitrogen, Carlsbad, CA, USA) for 2 h at room temperature (22 C).…”

Sirtuin 1-Chromatin-Binding Dynamics Points to a Common Mechanism Regulating Inflammatory Targets in SIV Infection and in the Aging Brain

“…A role for Sirt-1 in the brain has been proposed, in controlling blood brain barrier proteins and HIV infection in pericytes (Castro et al 2016). On the other hand, a potential ability of microglial Sirt-1 to control the onset of cognitive decline by affecting microglia and brain inflammatory components has been observed (Chen et al 2005; Cho et al 2015).…”