PMID: 30737283

Authors:

Liang M, Xie X, Pan J, Jin G, Yu C, Wei Z

Title:

Structural basis of the target-binding mode of the G protein-coupled receptor kinase-interacting protein in the regulation of focal adhesion dynamics.

Journal:

J Biol Chem. 2019 Feb 8. pii: RA118.006915. doi: 10.1074/jbc.RA118.006915.

Abstract:

Focal adhesions (FAs) are specialized sites where intracellular cytoskeleton elements connect to the extracellular matrix and thereby control cell motility. FA assembly depends on various scaffold proteins, including the G protein-coupled receptor kinase-interacting protein 1 (GIT1), paxillin and liprin-alpha. Although liprin-alpha and paxillin are known to competitively interact with GIT1, the molecular basis governing these interactions remains elusive. To uncover the underlying mechanisms of how GIT1 is involved in FAs assembly by alternatively binding to liprin-alpha and paxillin, here we solved the crystal structures of GIT1 in complex with liprin-alpha and paxillin at 1.8 A and 2.6 A resolutions, respectively. These structures revealed that the paxillin-binding domain (PBD) of GIT1 employs distinct binding modes to recognize a single alpha helix of liprin-alpha and the LD4 motif of paxillin. Structure-based design of protein variants produced two binding-deficient GIT1 variants; specifically, these variants lost the ability to interact with liprin-alpha only or with both liprin-alpha and paxillin. Expressing the GIT1 variants in COS7 cells, we discovered that the two PBD-meditated interactions play different roles in either recruiting GIT1 to FA or facilitating FA assembly. Additionally, we demonstrate that, unlike for the known binding mode of the FAT domain to LD motifs, the PBD of GIT1 uses different surface patches to achieve high selectivity in LD-motif recognition. In summary, our results have uncovered the mechanisms by which GIT1's PBD recognizes cognate paxillin and liprin-alpha structures, information we anticipate will be useful for future investigations of GIT1-protein interactions in cells.