title: Caveolin-1 regulates human immunodeficiency virus-1 Tat-induced alterations of tight junction protein expression via modulation of the Ras signaling.
abstract: The blood-brain barrier (BBB) is the critical structure for preventing human immunodeficiency virus (HIV) trafficking into the brain. Specific HIV proteins, such as Tat protein, can contribute to the dysfunction of tight junctions at the BBB and HIV entry into the brain. Tat is released by HIV-1-infected cells and can interact with a variety of cell surface receptors activating several signal transduction pathways, including those localized in caveolae. The present study focused on the mechanisms of Tat-induced caveolae-associated Ras signaling at the level of the BBB. Treatment with Tat activated the Ras pathway in human brain microvascular endothelial cells (HBMECs). However, caveolin-1 silencing markedly attenuated these effects. Because the integrity of the brain endothelium is regulated by intercellular tight junctions, these structural elements of the BBB were also evaluated in the present study. Exposure to Tat diminished the expression of several tight junction proteins, namely, occludin, zonula occludens (ZO)-1, and ZO-2 in the caveolar fraction of HBMECs. These effects were effectively protected by pharmacological inhibition of the Ras signaling and by silencing of caveolin-1. The present data indicate the importance of caveolae-associated signaling in the disruption of tight junctions on Tat exposure. They also demonstrate that caveolin-1 may constitute an early and critical modulator that controls signaling pathways leading to the disruption of tight junction proteins. Thus, caveolin-1 may provide an effective target to protect against Tat-induced HBMEC dysfunction and the disruption of the BBB in HIV-1-infected patients.
authors.affiliation: Molecular Neuroscience and Vascular Biology Laboratory, Department of Neurosurgery, University of Kentucky, Lexington, Kentucky 40536, USA.
authors.forename: Yu
authors.initials: Y
authors.lastname: Zhong
authors.forename: Eric J
authors.initials: EJ
authors.lastname: Smart
authors.forename: Babette
authors.initials: B
authors.lastname: Weksler
authors.forename: Pierre-Olivier
authors.initials: PO
authors.lastname: Couraud
authors.forename: Bernhard
authors.initials: B
authors.lastname: Hennig
authors.forename: Michal
authors.initials: M
authors.lastname: Toborek
mesh_terms: D000818:Animals; D051242:Caveolin 1 / Q000037:antagonists & inhibitors / Q000172:deficiency / Q000235:genetics / Q000502:physiology*; D002461:Cell Line, Transformed; D015967:Gene Expression Regulation, Viral; D015497:HIV-1 / Q000502:physiology*; D006801:Humans; D008565:Membrane Proteins / Q000096:biosynthesis / Q000235:genetics / Q000502:physiology*; D051379:Mice; D008810:Mice, Inbred C57BL; D018345:Mice, Knockout; D010750:Phosphoproteins / Q000096:biosynthesis / Q000235:genetics / Q000502:physiology*; D015398:Signal Transduction / Q000235:genetics; D062826:Zonula Occludens-1 Protein; D018631:ras Proteins / Q000502:physiology*; D054322:tat Gene Products, Human Immunodeficiency Virus / Q000502:physiology*
chemical_list: C495540:CAV1 protein, human; D051242:Caveolin 1; D008565:Membrane Proteins; D010750:Phosphoproteins; C569042:TJP1 protein, human; C569043:Tjp1 protein, mouse; D062826:Zonula Occludens-1 Protein; D054322:tat Gene Products, Human Immunodeficiency Virus; D018631:ras Proteins