Regular Articles
Chloride Intracellular Channel Protein-4 Functions in Angiogenesis by Supporting Acidification of Vacuoles Along the Intracellular Tubulogenic Pathway

https://doi.org/10.2353/ajpath.2009.080625Get rights and content

Endothelial cells form capillary tubes through the process of intracellular tubulogenesis. Chloride intracellular channel (CLIC) family proteins have been previously implicated in intracellular tubulogenesis, but their specific role has not been defined. In this study, we show that disruption of the Clic4 gene in mice results in defective angiogenesis in vivo as reflected in a Matrigel plug angiogenesis assay. An angiogenesis defect is also apparent in the retina, both in the decreased spontaneous development of retinal vasculature of unstressed mice and in the dramatically decreased angiogenic response of retinal vessels to an oxygen toxicity challenge. We found that endothelial cells derived from Clic4−/− mice demonstrated impaired tubulogenesis in three-dimensional fibrin gels compared with cells derived from wild-type mice. Furthermore, we found that tubulogenesis of wild-type cells in culture was inhibited by both an inhibitor of CLICs and an inhibitor of the vacuolar proton ATPase. Finally, we showed that vacuoles along the endothelial tubulogenesis pathway are acidic in wild-type cells, and that vacuolar acidification is impaired in Clic4−/− cells while lysosomal acidification is intact. We conclude that CLIC4 plays a critical role in angiogenesis by supporting acidification of vacuoles along the cell-hollowing tubulogenic pathway.

Cited by (0)

Supported by the Department of Veterans Affairs (merit award to J.C.E.), the National Institutes of Health (grants RO1 DK060551 to J.C.E. and R01 EY015130 to M.E.H.), and the Research to Prevent Blindness (to M.E.H.).

View Abstract