ADAM13 Function in Development

ADAM13 is a cell surface metalloprotease containing a disintegrin domain. It was cloned in an effort to identify ADAM proteins that function during early embryogenesis in the frog Xenopus laevis. ADAM13 is most similar in sequence to the meltrins (ADAM12, 19 and 33) and is expressed as a zygotic messenger RNA at the Mid Blastula Transition (MBT). The protein is expressed in Cranial Neural Crest (CNC) cells and somites during neurulation and subsequent tailbud formation. ADAM13 is a protease that can cleave itself and the extracellular matrix (ECM) protein fibronectin. Xenopus XTC cells expressing ADAM13 can remodel a fluorescent fibronectin substrate while cells expressing a dominant negative form of ADAM13 cannot. The adhesive domain of ADAM13 (DC) binds to the heparin-binding domain of fibronectin at the same site as the proteoglycan syndecan. Mutations in fibronectin that abolish syndecan binding also prevent ADAM13 association. The proteolytic activity of ADAM13 is essential for CNC migration in two of the three main pathways (Branchial and Hyoid but not Mandibular), while this activity is not essential for CNC migration in vitro. ADAM13 proteolytic specificity depends on the adhesive region of the extracellular domain (DC) rather than on the metalloprotease domain. Finally, ADAM13 activity is controlled by two specific regions of its cytoplasmic domain. The juxtamembrane domain controls protein level while the proline-rich carboxyl terminal region binds to proteins containing an SH3-domain. One of these SH3-containing proteins, PACSIN-2, binds to and down regulates ADAM13 proteolytic function in embryos.