27, 2011; Accepted May 9, 2011; Published June 13, 2011 Copyright: 2011 Asperti et al. This is an open-access article distributed under the terms of the Creative Commons Attribution License, which permits unrestricted use, distribution, and reproduction in any medium, provided the original author and source are credited. Funding: The following sources of funding to Ivan de Curtis have supported this work: AIRC, Italian Asssociation for Cancer Research, grant n.10321 Fondazione Cariplo Telethon–Italy, grant GGP09078. Moreover, a fellowship from FIRC, Italian Foundation for Cancer Research supported Veronica Astro. The funders had no role in study design, data collection and analysis, decision to publish, or preparation of the manuscript. Competing Interests: The authors have declared that no competing interests exist. E-mail: [email protected]. These authors contributed equally to this work. Introduction Cell BGJ 398 site migration requires complex molecular events that need to be finely regulated in time and space. GIT1 and GIT2/PKL form a family of multi-domain ArfGAP proteins with scaffolding activity, which are implicated in the regulation of cell adhesion and migration on extracellular matrix. They interact via an SHD with the components of the PIX family of guanine nucleotide exchanging factors for Rac and Cdc42 GTPases. Moreover, the carboxy-terminal region of GIT proteins can interact with the adaptor proteins paxillin and liprin-a1, both implicated in the formation and turnover of integrinmediated FAs . GIT proteins are involved in different pathways that regulate cell motility. For example, GIT1 is involved in EGF-dependent vascular smooth muscle cell migration, while the second member of the family, GIT2 is a key player for chemotactic directionality in stimulated neutrophils, and is required for PDGF-dependent directional cell migration and cell polarity, but not for random migration. It has been proposed that GIT1 may cycle between at least three distinct subcellular compartments, including FAs, leading edge, and cytoplasmic compartments, and the functional interaction between GIT1, bPIX and PAK 18288792 has been associated to cell protrusive activity 
and migration. On the other hand, the precise function of the GIT complexes in cell motility is still insufficiently understood, and existing findings have led to conflicting reports on whether the recruitment of GIT-mediated complexes positively or negatively affect Rac-mediated protrusion. The localization of GIT1 at the leading edge may play a role in recruiting the GTPase activator bPIX and the Rac effector PAK at the same location, thus restricting the activity of Rac1 to the front of motile cells where actin assembly is needed. It has June 2011 | Volume 6 | Issue 6 | e20757 Liprin-a1 and GIT1 Regulate Migration been shown that GIT1 regulates the protrusive activity at the cell border, and that the GIT1/PIX/PAK complex is recruited by the FA protein paxillin at dynamic peripheral adhesive structures to regulate their turnover. Liprins are a family of scaffold proteins that include the liprin-a and -b subfamilies. Liprin-a proteins are multi-domain proteins that can interact directly with several binding partners. Recent work has revealed that liprin-a1 is an essential regulator of cell motility and tumor cell invasion but the exact implication and role of the different liprin-a/partner complexes in the regulation of cell motility are poorly understood. We have shown that the interaction of
