Abstract
Our previous work indicated that cytoskeletal association may regulate the redistribution of PECAM1 on the surface of human endothelial cells after treatment with TNFα or IFNγ (Journal of Immunology 154:65826592, 1995). We have, therefore, investigated PECAM1 interactions with cytoskeletal proteins. Immunofluorescence studies indicated that PECAM1 colocalized with cytoskeletal proteins between Factin arrays and the plasma membrane in human umbilical vein endothelial cell (HUVEC) monolayers, Multiple interdigitations and irregularities in the intercellular appearance of PECAM1 were found to correspond with the configuration of the Factin at the cells' perimeters. This pattern of intercellular localization appeared to correspond with staining for alphaactinin, filamin, talin, and vinculin. These cytoskeletal proteins and the actinbinding protein cortactin were all investigated by immunoprecipitation for evidence of biochemical interaction with PECAM1. AntiPECAM1 immunoprecipitates from whole cell lysates of confluent HUVEC monolayers were analyzed by SDSPAGE and immunoblotting. They were found to contain talin. Alphaactinin, cortactin, filamin, and vinculin were not reproducibly identified in these PECAM1 immunoprecipitates. The reverse analysis was also performed in each case. Immunoblot analyses of antialphaactinin, anticortactin, antifilamin, and antivinculin immunoprecipitates from HUVEC lysates were negative for PECAM1. PECAM1 did appear in antitalin immunoprecipitates from confluent, but not subconfluent, HUVEC monolayers. These experiments indicate that PECAM1 may associate with the cytoskeletal protein talin in normal human vascular endothelium. The role of talin in the regulation of the intercellular localization of PECAM1 is under investigation.
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