Abstract
Protease-activated receptor 1 (PAR1) is a G protein-coupled receptor for thrombin. In addition to active Src by G protein, PAR1 recruits Src by □-arrestin to transduce signals. Src is then sorted to lysosomes with the activated PAR1 for degradation. However, the mechanism by which PAR1-induced degradation of Src and the receptor itself is still unclear. It has been reported that degradation of active Src is mediated by c-Cbl, an ubiquitin E3 ligase. To determine whether c-Cbl mediates the degradation of Src and PAR1 after receptor activation, CHO-K1 cells stably expressing FLAG-tagged PAR1 were transiently transfected with a dominant negative c-Cbl mutant to examine its effect on the degradation of Src and PAR1. I found that stimulation of PAR1 induced degradation of Src. The degradation of Src was blocked by chloroquine, a lysosomal inhibitor. The dominant negative c-Cbl mutant lacking the RING-finger domain (□RF c-Cbl) inhibited PAR1-induced degradation of Src and partially inhibited the degradation of PAR1. However, □RF c-Cbl did not affect the endocytosis of PAR1. Taken together, these results indicated that c-Cbl mediated lysosomal degradation of Src and PAR1 after the receptor activation.