| Using the cytosolic C terminal region of C5aR as bait to screen a human leucocyte cDNA library , we identified the Wiskott Aldrich syndrome protein ( WASP ) as a potential partner of C5aR . ^^^ The interaction between C5aR and the WASP . 321 was supported further by an in vitro binding assay between a radiolabelled WASP . 321 fragment and a receptor C terminus glutathione S transferase ( GST ) fusion protein , as well as by GST pull down , co immunoprecipitation and immunofluorescence experiments . ^^^ In the yeast two hybrid assay , full length WASP showed no ability to interact with the C terminal domain of C5aR . ^^^ In HEK 293T cells co transfected with full length WASP and C5aR , only a small amount of WASP was co precipitated with the receptor . ^^^ We hypothesize that a transient interaction between C5aR and WASP occurs following the stimulation of C5aR and Cdc 42 activation . ^^^ |