Lipid rafts regulate PCB153-induced disruption of occludin and brain endothelial barrier function through protein phosphatase 2A and matrix metalloproteinase-2

Abstract

Occludin is an essential integral transmembrane protein regulating tight junction (TJ) integrity in brain endothelial cells. Phosphorylation of occludin is associated with its localization to TJ sites and incorporation into intact TJ assembly. The present study is focused on the role of lipid rafts in polychlorinated biphenyl (PCB)-induced disruption of occludin and endothelial barrier function. Exposure of human brain endothelial cells to 2,2′,4,4′,5,5′-hexachlorobiphenyl (PCB153) induced dephosphorylation of threonine residues of occludin and displacement of occludin from detergent-resistant membrane (DRM)/lipid raft fractions within 1 h. Moreover, lipid rafts modulated the reduction of occludin level through activation of matrix metalloproteinase 2 (MMP-2) after 24 h h PCB153 treatment. Inhibition of protein phosphatase 2A (PP2A) activity by okadaic acid or fostriecin markedly protected against PCB153-induced displacement of occludin and increased permeability of endothelial cells. The implication of lipid rafts and PP2A signaling in these processes was further defined by co-immunoprecipitation of occludin with PP2A and caveolin-1, a marker protein of lipid rafts. Indeed, a significant MMP-2 activity was observed in lipid rafts and was increased by exposure to PCB153. The pretreatment of MMP-2 inhibitors protected against PCB153-induced loss of occludin and disruption of lipid raft structure prevented the increase of endothelial permeability. Overall, these results indicate that lipid raft-associated processes, such as PP2A and MMP-2 activation, participate in PCB153-induced disruption of occludin function in brain endothelial barrier. This study contributes to a better understanding of the mechanisms leading to brain endothelial barrier dysfunction in response to exposure to environmental pollutants, such as ortho-substituted PCBs.

Circadian disruption alters gut barrier integrity via a ß-catenin-MMP-related pathway

“…MMP-2/9 specifically are gelatinases that activate pro-inflammatory agents and mediate TJ protein degradation [ 66 , 67 ]. Our observations are in agreement with the involvement of MMPs in the regulation of tissue barrier integrity as shown previously by us [ 68 ] and others [ 69 ]. ß-catenin has been linked to MMP-2/9 in epithelial cells via negative regulation as inhibition of Wnt/ß-catenin signaling led to increases in extracellular matrix metalloproteinase inducer (EMMPRIN) and MMP-2/9.…”

Circadian Disruption Alters Gut Barrier Integrity via a ß-catenin-MMP-related Pathway

“…MMP-2/9 specifically are gelatinases that activate proinflammatory agents and mediate TJ protein degradation 62,63 . Our observations are in agreement with the involvement of MMPs in the regulation of tissue barrier integrity as shown previously by us 64 and others 65 . ß-catenin has been linked to MMP-2/9 in epithelial cells via negative regulation as inhibition of Wnt/ß-catenin signaling led to increases in EMMPRIN, an extracellular MMP inducer, and MMP-2/9.…”

Comparative Analysis of Single-Molecule Dynamics of TRPV1 and TRPV4 Channels in Living Cells

“…The calcineurin-dependent dephosphorylation of TRPV1 [37] and the PIP 2 depletion from the membrane [35] was proposed as mechanisms of the desensitization. Considering that the calcineurin was predominantly present in non-lipid raft domains [38], the present results propose a hypothesis that the membrane domain localization of TRPV1 spatially controls the balance between the Ca 2+ -dependent phosphorylation and dephosphorylation. The VB-HMM analysis suggested that TRPV1 molecules are in dynamic transition among three diffusion states with subsecond time constants (Figure S15).…”