Cloning and sequencing of cDNA encoding mouse cytohesin-1

Cytohesin-1 has recently been identified as a potential regulatory molecule for LFA-1 in human T cells. Cytohesin-1 is a cytoplasmic protein containing a Sec7 domain and a pleckstrin homology (PH) domain, and is encoded by cDNA previously identified in natural killer and cytotoxic T cells. In the human T-cell leukemia cell line Jurkat, overexpression of full-length cytohesin-1 or the isolated Sec7 domain gave rise to constitutive activation of LFA-1; conversely, over-expression of the PH domain-inhibited TCR-activated LFA-1 adhesion to ICAM-1. These findings strongly suggest that cytohesin-1 plays a role in the physiological regulation of T-cell adhesion through LFA-1.