Tight junctions are membrane microdomains

Abstract

Tight junctions (TJ) of polarized epithelial cells regulate barrier function at mucosal surfaces. Structural proteins of TJs include hyperphosphorylated occludin (HO) and the peripheral membrane protein, ZO-1. Since TJs are dynamically regulated, and lipid-modified signal transduction proteins localize to TJs, we considered the possibility that the TJ itself is composed of microdomains with unique structure. Differential detergent extraction and isopycnic sucrose density gradients were utilized to isolate TJ-enriched membranes from a polarized intestinal epithelial cell line, T84. Here we report that major pools of hyperphosphorylated occludin (HO) and ZO-1 are found in raft-like membrane microdomains with characteristics of the previously described detergent-insoluble glycolipid rafts (DIGs). Properties of such gradient fractions included Triton X-100 (TX-100) insolubility, light scattering at 600 nm, buoyant density of approximately 1.08 g/cm(3) and increased cholesterol content compared to high density fractions. Similar results were obtained using natural epithelium. Unlike the TJ proteins HO and ZO-1, other basolateral transmembrane proteins including E-cadherin, c-met and β 1 integrin were not increased in DIG-like fractions. Immunoprecipitation studies revealed coprecipitation of a pool of occludin with caveolin-1, a scaffolding protein abundant in DIGs. Coprecipitation results were supported by immunofluorescence and immunogold labeling studies demonstrating caveolin-1 localization in the apical membrane and focal colocalization with occludin in TJs. TJ disassembly by calcium chelation resulted in displacement of TJ proteins from the ‘raft-like’ compartment. Our findings suggest that raft-like compartments play an important role in the spatial organization of TJs and probably in regulation of paracellular permeability in epithelial cells.

Dietary dimethylglycine sodium salt supplementation alleviates redox status imbalance and intestinal dysfunction in weaned piglets with intrauterine growth restriction

“…Intrauterine growth restriction leads to intestinal diseases in the perinatal period and predisposes individuals to feeding intolerance and digestive diseases in the early postnatal period ( Bernstein et al., 2000 ). The movement of substances across the cell membrane depends on diffusion or active transport, which depend on the intestinal structure ( Nusrat et al., 2000 ). Consistent with our study, it has shown that intrauterine growth restriction leads to intestinal villus atrophy, mucosal oxidative damage, and intestinal dysfunction, thereby causing diarrhea and reduction in feed utilization in piglets ( Wang et al., 2005 , 2008 ).…”

Altered Blood Brain Barrier Permeability and Oxidative Stress in Cntnap2 Knockout Rat Model

“…ZO-1 is one of the major tight junction proteins that facilitates in maintaining the BBB integrity. ZO-1 can help in predicting the healthy and pathological state of the BBB, making it a valuable marker of the endothelial barrier [ 97 ]. Decreased expression and disarrangement of ZO-1 has been associated with an increase in BBB permeability [ 98 ].…”

Role of Barrier Integrity and Dysfunctions in Maintaining the Healthy Gut and Their Health Outcomes

“…It affects the organization of TJ proteins . Some studies demonstrate that it is also responsible for redistribution of lipid microdomain proteins like flotillin1 and caveolin1 (Nusrat et al, 2000; which are associated with TJ membrane integrity. Researchers demonstrated that Kaempferol swiftly and significantly elevated the TEER values of the Caco-2 cells, but surprisingly they did not disturbed the membrane permeability.…”