CALP1 is a calmodulin (CaM) agonist (Kd of 88 µM) with binding to the CaM EF-hand/Ca2+-binding site. CALP1 blocks calcium influx and apoptosis (IC50 of 44.78 µM) through inhibition of calcium channel opening. CALP1 blocks glutamate receptor channels and blocks a store-operated nonselective cation channel. CALP1 activates CaM-dependent phosphodiesterase activity[1][2][3][4].