Stimulation of cleavage of membrane proteins by calmodulin inhibitors.
The ectodomain of several membrane-bound proteins can be shed by proteolytic cleavage. The activity of the proteases involved in shedding is highly regulated by several intracellular second messenger pathways, such as protein kinase C (PKC) and intracellular Ca(2+). Recently, the shedding of the adhesion molecule L-selectin has been shown to be regulated by the interaction of calmodulin (CaM) with the cytosolic tail of L-selectin. Prevention of CaM-L-selectin interaction by CaM inhibitors or mutation of a CaM binding site in L-selectin induced L-selectin ectodomain shedding. Whether this action of CaM inhibitors also affects other membrane-bound proteins is not known. In the present paper we show that CaM inhibitors also stimulate the cleavage of several other transmembrane proteins, such as the membrane-bound growth factor precursors pro-transforming growth factor-alpha and pro-neuregulin-alpha2c, the receptor tyrosine kinase, TrkA, and the beta-amyloid precursor protein. Cleavage induced by CaM inhibitors was a rapid event, and resulted from the activation of a mechanism that was independent of PKC or intracellular Ca(2+) increases, but was highly sensitive to hydroxamic acid-based metalloprotease inhibitors. Mutational analysis of the intracellular domain of the TrkA receptor indicated that CaM inhibitors may stimulate membrane-protein ectodomain cleavage by mechanisms independent of CaM-substrate interaction.
Díaz-Rodríguez
E
E
Instituto de Microbiología Bioquímica, Edificio Departamental, Consejo Superior de Investigaciones Científicas-Universidad de Salamanca, Avenida del Campo Charro s/n, 37007-Salamanca, Spain.
Esparís-Ogando
A
A
Montero
J C
JC
Yuste
L
L
Pandiella
A
A
D000818:Animals; D002147:Calmodulin / Q000037:antagonists & inhibitors*; D002460:Cell Line; D006801:Humans; D008565:Membrane Proteins / Q000737:chemistry* / Q000378:metabolism*; D008666:Metalloendopeptidases / Q000378:metabolism*; D010447:Peptide Hydrolases / Q000737:chemistry / Q000378:metabolism
D002147:Calmodulin; D008565:Membrane Proteins; D010447:Peptide Hydrolases; D008666:Metalloendopeptidases