• Jun Zhang, Sharmila Basu, Daniele Rigamonti, Harry C Dietz, and Richard E Clatterbuck.
• Department of Neurosurgery, University of Mississippi Medical Center, Jackson, Mississippi 39216-4505, USA. jhzhang@neurosurgery.umsmed.edu
• Neurosurgery. 2008 Sep 1; 63 (3): 571-8; discussion 578.

ObjectiveUsing ribonucleic acid interference on cultured cell lines, we examined the role of Krev interaction trapped 1 (krit1) and integrin cytoplasmic domain-associated protein-1 alpha (icap1alpha) in beta1-integrin-mediated cell proliferation.MethodsUpon depletion of either krit1 or icap1alpha in the HeLa cells, umbilical vein endothelial cells, and microvascular endothelial cells, we examined the cell number and proliferation changes in the cells, followed by the evaluation of beta1-integrin-mediated mitogen-activated protein kinase signal pathway and microscopic study.ResultsDepletion of krit1 reduces cell number and decreases endothelial cell proliferation. Examination of beta1-integrin signaling downstream of focal adhesion kinase reveals decreased phosphorylation along the extracellular signal-regulated kinase/mitogen-activated protein kinase pathway. Depletion of icap1alpha, a protein known to interact with krit1, has similar effects, suggesting synergistic function. We also show that krit1 colocalizes with icap1alpha in both the nucleus and the cytoplasm; however, most of icap1alpha is found in the nucleus and most of krit1 is found in the cytoplasm at steady state. On depletion of krit1, icap1alpha decreases in the cytoplasm and is no longer detected in the nucleus.ConclusionBoth krit1 and icap1alpha act concordantly to play a critical role in beta1-integrin-mediated cell proliferation. Our data further suggest that krit1 both stabilizes and shuttles icap1alpha and thus modulates its regulation of beta1-integrin-mediated signal transduction.

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