CUTTING EDGE - DIFFERENTIAL CD5-DEPENDENT REGULATION OF CD5-ASSOCIATED CK2 ACTIVITY IN MATURE AND IMMATURE T-CELLS - IMPLICATION ON TCR CD3-MEDIATED ACTIVATION/

CD5 attenuates TCR-induced signals in immature thymocytes but function s as a costimulatory molecule potentiating TCR/CD3-mediated activation in mature, peripheral T cells, We have recently shown that the serine /threonine kinase, casein kinase 2 (CK2), a major regulator of cell gr owth and signaling, associates with and is activated by CD5, Therefore , we tested the possibility that differential regulation of CK2 activi ty by CD5 may be associated with these differences in CD5 modulation o f TCR signaling. Consistent with our hypothesis, CD5-specific cross-li nking activated associated CK2 in thymocytes but not active in mature splenocytes, Differential regulation of CD5-associated CK2 provides, f or the first time, a potential mechanism for the differential effects of CD5 signaling in immature and mature cells. We propose that CD5 mod ulates Ag receptor activity through developmentally regulated activati on of CD5-associated CK2.