Acute lung injury (ALI) and acute respiratory distress syndrome currently affect ~200,000 Americans annually, with ~40% resulting in mortality. Vascular permeability, a major hallmark of acute lung injury, is regulated by cell-cell contact at the interendothelial junction. VE-cadherin, a key component of adherens junctions (AJ), homodimerizes at the interendothelial junction (IEJ) to strengthen the barrier integrity of microvascular endothelial cells. Endocytotic trafficking of VE-cadherin, which results in recycling to the IEJ or lysosomal degradation, is vital in the maintenance of endothelial barrier function. Rab GTPases are responsible for the spatial and temporal distribution of endosomes within the cell; specifically the association of Rab4 and 11 with the early endosome enhances recycling whilst Rab7 and 9 association with the early endosome directs it to the lysosome for degradation. A novel protein, p18, has recently been identified to play a key role in endocytosis, although its role on VE-cadherin or endothelial barrier function has yet to be elucidated. Our preliminary data indicates that p18 overexpression reduces internalization of VE-cadherin and improves endothelial barrier function, both under baseline conditions and in settings of ALI. Thus we hypothesize that p18 regulates Rab-mediated intracellular trafficking of VE-cadherin by elevating recycling and reducing lysosomal degradation of VE-cadherin-positive endosomes. We postulate that targeting endocytotic trafficking of VE-cadherin, specifically lysosomal degradation, will represent a novel therapeutic treatment for acute lung injury. The specific aims of this proposal are therefore; i) to determine if p18 stabilizes AJs through regulation of VE-cad+ endosomes trafficking to IEJ, ii) to determine if Rab GTPase-mediated trafficking of VE-cad is regulated via p18 in settings of ALI, and iii) to determine if Src-mediated phosphorylation of p18 shifts the Rab-p18 axis to alter the fate of VE-cad+ endosomes in settings of ALI. By establishing the mechanism through which p18 regulates endocytosis, we hope to implicate the endosome as a novel therapeutic target in the treatment of ALI.
|Program type||Postdoctoral Fellowship|
|Effective start/end date||07/01/2013 → 04/07/2015|