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Paxillin phosphorylation at Ser273 localizes a GIT1-PIX-PAK complex and regulates adhesion and protrusion dynamics.

ABSTRACT: Continuous adhesion formation and disassembly (adhesion turnover) in the protrusions of migrating cells is regulated by unclear mechanisms. We show that p21-activated kinase (PAK)-induced phosphorylation of serine 273 in paxillin is a critical regulator of this turnover. Paxillin-S273 phosphorylation dramatically increases migration, protrusion, and adhesion turnover by increasing paxillin-GIT1 binding and promoting the localization of a GIT1-PIX-PAK signaling module near the leading edge. Mutants that interfere with the formation of this ternary module abrogate the effects of paxillin-S273 phosphorylation. PAK-dependent paxillin-S273 phosphorylation functions in a positive-feedback loop, as active PAK, active Rac, and myosin II activity are all downstream effectors of this turnover pathway. Finally, our studies led us to identify in highly motile cells a class of small adhesions that reside near the leading edge, turnover in 20-30 s, and resemble those seen with paxillin-S273 phosphorylation. These adhesions appear to be regulated by the GIT1-PIX-PAK module near the leading edge.

SUBMITTER: Nayal A

PROVIDER: S-EPMC2063867 | biostudies-literature | 2006 May

REPOSITORIES: biostudies-literature

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Paxillin phosphorylation at Ser273 localizes a GIT1-PIX-PAK complex and regulates adhesion and protrusion dynamics.

Nayal Anjana A Webb Donna J DJ Brown Claire M CM Schaefer Erik M EM Vicente-Manzanares Miguel M Horwitz Alan Rick AR

The Journal of cell biology 20060501 4

Continuous adhesion formation and disassembly (adhesion turnover) in the protrusions of migrating cells is regulated by unclear mechanisms. We show that p21-activated kinase (PAK)-induced phosphorylation of serine 273 in paxillin is a critical regulator of this turnover. Paxillin-S273 phosphorylation dramatically increases migration, protrusion, and adhesion turnover by increasing paxillin-GIT1 binding and promoting the localization of a GIT1-PIX-PAK signaling module near the leading edge. Mutan ...[more]

PMID: 16717130

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Project description:Focal adhesions are protein complexes that anchor cells to the extracellular matrix. During migration, the growth and disassembly of these structures are spatiotemporally regulated, with new adhesions forming at the leading edge of the cell and mature adhesions disassembling at the rear. Signalling proteins and structural cytoskeletal components tightly regulate adhesion dynamics. Paxillin, an adaptor protein within adhesions, is one of these proteins. Its phosphorylation at serine 273 (S273) is crucial for maintaining fast adhesion assembly and disassembly. Paxillin is known to bind to a GIT1-?PIX-PAK1 complex, which increases the local activation of the small GTPase Rac. To understand quantitatively the behaviour of this system and how it relates to adhesion assembly/disassembly, we developed a mathematical model describing the dynamics of the small GTPases Rac and Rho as determined by paxillin S273 phosphorylation. Our model revealed that the system possesses bistability, where switching between uninduced (active Rho) and induced (active Rac) states can occur through a change in rate of paxillin phosphorylation or PAK1 activation. The bistable switch is characterized by the presence of memory, minimal change in the levels of active Rac and Rho within the induced and uninduced states, respectively, and the limited regime of monostability associated with the uninduced state. These results were validated experimentally by showing the presence of bimodality in adhesion assembly and disassembly rates, and demonstrating that Rac activity increases after treating Chinese Hamster Ovary cells with okadaic acid (a paxillin phosphatase inhibitor), followed by a modest recovery after 20 min washout. Spatial gradients of phosphorylated paxillin in a reaction-diffusion model gave rise to distinct regions of Rac and Rho activities, resembling polarization of a cell into front and rear. Perturbing several parameters of the model also revealed important insights into how signalling components upstream and downstream of paxillin phosphorylation affect dynamics.

Dataset Information

Paxillin phosphorylation at Ser273 localizes a GIT1-PIX-PAK complex and regulates adhesion and protrusion dynamics.

Publications

Paxillin phosphorylation at Ser273 localizes a GIT1-PIX-PAK complex and regulates adhesion and protrusion dynamics.

Similar Datasets

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