Association of T cell antigen CD7 with type II phosphatidylinositol‐4 kinase, a key component in pathways of inositol phosphate turnover

Abstract

CD7 is a 40‐kDa glycoprotein that is expressed on prothymocytes and persists during T cell differentiation. CD7 has been demonstrated to generate, like other costimulatory molecules, intracellular signals that modulate T cell function. However, although it binds to phosphatidylinositol 3‐kinase (PI 3‐kinase), the signaling events mediated by CD7 are not completely understood. In this context, phosphatidylinositol 4‐kinase (PI 4‐kinase) is a key enzyme involved in a variety of events, from the modeling of the actin cytoskeleton to the activation of protein kinase C. In this study, we show for the first time that PI 4‐kinase of 55 kDa can associate with CD7. The enzyme activity was insensitive to wortmannin, but was inhibited by adenosine, a characteristic for type II PI 4‐kinase. Together, our findings demonstrate that type II PI 4‐kinases are integral components of the CD7 signaling pathway and may play a role of CD7 in co‐stimulation and thymic differentiation.