Functional analysis of the cytoplasmic domain of the integrin α1 subunit in endothelial cells

Abstract

AbstractIntegrin α1β1, the major collagen type IV receptor, is expressed by endothelial cells and plays a role in both physiologic and pathologic angiogenesis. Because the molecular mechanisms whereby this collagen IV receptor mediates endothelial cell functions are poorly understood, truncation and point mutants of the integrin α1 subunit cytoplasmic tail (amino acids 1137-1151) were generated and expressed into α1-null endothelial cells. We show that α1-null endothelial cells expressing the α1 subunit, which lacks the entire cytoplasmic tail (mutant α1-1136) or expresses all the amino acids up to the highly conserved GFFKR motif (mutant α1-1143), have a similar phenotype to parental α1-null cells. Pro1144 and Leu1145 were shown to be necessary for α1β1-mediated endothelial cell proliferation; Lys1146 for adhesion, migration, and tubulogenesis and Lys1147 for tubulogenesis. Integrin α1β1–dependent endothelial cell proliferation is primarily mediated by ERK activation, whereas migration and tubulogenesis require both p38 MAPK and PI3K/Akt activation. Thus, distinct amino acids distal to the GFFKR motif of the α1 integrin cytoplasmic tail mediate activation of selective downstream signaling pathways and specific endothelial cell functions.