GSK3 and Polo-like kinase regulate ADAM13 function during cranial neural crest cell migration.

ADAMs are cell surface metalloproteases that control multiple biological processes by cleaving signaling and adhesion molecules. ADAM13 controls Cranial Neural Crest (CNC) cell migration both by cleaving Cadherin-11 to release a promigratory extracellular fragment and by controlling multiple genes' expression via its cytoplasmic domain. The latter activity is regulated by γ-secretase cleavage and the translocation of the cytoplasmic domain into the nucleus. One of the genes regulated by ADAM13, the protease Calpain8, is essential for CNC migration. While the nuclear function of ADAM13 is evolutionarily conserved, it is unclear if the transcriptional regulation is also performed by other ADAMs and how this process may be regulated. We show that ADAM13 function to promote CNC migration is regulated by two phosphorylation events involving GSK3 and Polo-like kinase (Plk). We further show that inhibition of either kinase blocks CNC migration and that the respective phosphomimetic forms of ADAM13 can rescue these inhibitions. However, these phosphorylations are not required for ADAM13 proteolysis of its substrates, γ-secretase cleavage or nuclear translocation of its cytoplasmic domain. Significantly, migration of the CNC can be restored in the absence of Plk phosphorylation by expression of Calpain-8a, pointing to an impaired nuclear activity of ADAM13.