Interaction of the metalloprotease disintegrins MDC9 and MDC15 with two SH3 domain-containing proteins, endophilin I and SH3PX1

Metalloprotease disintegrins (a disintegrin and metalloprotease (ADAM) and metalloprotease, disintegrin, cysteine-rich proteins (MDC)) are a family of membrane-anchored glycoproteins that function in diverse biological proces ses, including fertilization, neurogenesis, myogenesis, and ectodomain proc essing of cytokines and other proteins. The cytoplasmic domains of ADAMs of ten include putative signaling motifs, such as proline-rich SH3 ligand doma ins, suggesting that interactions with cytoplasmic proteins may affect meta lloprotease disintegrin function. Here we report that two SH3 domain-contai ning proteins, endophilin I (SH3GL2, SH3p4) and a novel SH3 domain- and pho x homology (PX) domain-containing protein, termed SH3PX1, can interact with the cytoplasmic domains of the metalloprotease disintegrins MDC9 and MDC15 . These interactions were initially identified in a yeast two-hybrid screen and then confirmed using bacterial fusion proteins and co-immunoprecipitat ions from eukaryotic cells expressing both binding partners. SHSPX1 and end ophilin I both preferentially bind the precursor but not the processed form of MDC9 and MDC15 in COS-7 cells. Since rat endophilin I is thought to pla y a role in synaptic vesicle endocytosis and SH3PX1 has sequence similarity to sorting nexins in yeast, we propose that endophilin I and SH3PX1 may ha ve a role in regulating the function of MDC9 and MDC15 by influencing their intracellular processing, transport, or final subcellular localization.