Regulation of Cdc42 Gtpase by Proline-Rich Tyrosine Kinase 2 Interacting with Psgap, a Novel Pleckstrin Homology and Src Homology 3 Domain Containing Rhogap Protein

Proline-rich tyrosine kinase 2 (PYK2), a tyrosine kinase structurally related to focal adhesion kinase (FAK), is implicated in regulating cytoskeletal organization. However, mechanisms by which PYK2 participates in and regulates cytoskeletal organization remain largely unknown. Here we report identification of PSGAP, a novel protein that interacts with PYK2 and FAK and contains multiple domains including a pleckstrin homology domain, a rhoGTPase-activating protein domain, and a Src homology 3 domain. PYK2 interacts with PSGAP Src homology 3 domain via the carboxyl-terminal proline-rich sequence. PSGAP is able to increase GTPase activity of CDC42 and RhoA in vitro and in vivo. Remarkably, PYK2, but not FAK, can activate CDC42 via inhibition of PSGAP-mediated GTP hydrolysis of CDC42. Moreover, PSGAP is localized at cell periphery in fibroblasts in a pleckstrin homology domain–dependent manner. Over expression of PSGAP in fibroblasts results in reorganization of cytoskeletal structures and changes of cellular morphology, which requires rhoGTPase-activating activity. Taken together, our results suggest that PSGAP is a signaling protein essential for PYK2 regulation of cytoskeletal organization via Rho family GTPases.

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Regulation of the formation of osteoclastic actin rings by proline-rich tyrosine kinase 2 interacting with gelsolin

The Journal of Cell Biology ◽

10.1083/jcb.200207036 ◽

2003 ◽

Vol 160 (4) ◽

pp. 565-575 ◽

Cited By ~ 71

Author(s):

Qiang Wang ◽

Yi Xie ◽

Quan-Sheng Du ◽

Xiao-Jun Wu ◽

Xu Feng ◽

...

Keyword(s):

Cell Adhesion ◽

Tyrosine Kinase ◽

Actin Polymerization ◽

Actin Binding ◽

Cell Periphery ◽

Cytoskeletal Organization ◽

Capping Protein ◽

Tyrosine Kinase 2 ◽

Multiple Cells ◽

Actin Rings

Osteoclast activation is important for bone remodeling and is altered in multiple bone disorders. This process requires cell adhesion and extensive actin cytoskeletal reorganization. Proline-rich tyrosine kinase 2 (PYK2), a major cell adhesion–activated tyrosine kinase in osteoclasts, plays an important role in regulating this event. The mechanisms by which PYK2 regulates actin cytoskeletal organization and osteoclastic activation remain largely unknown. In this paper, we provide evidence that PYK2 directly interacts with gelsolin, an actin binding, severing, and capping protein essential for osteoclastic actin cytoskeletal organization. The interaction is mediated via the focal adhesion–targeting domain of PYK2 and an LD motif in gelsolin's COOH terminus. PYK2 phosphorylates gelsolin at tyrosine residues and regulates gelsolin bioactivity, including decreasing gelsolin binding to actin monomer and increasing gelsolin binding to phosphatidylinositol lipids. In addition, PYK2 increases actin polymerization at the fibroblastic cell periphery. Finally, PYK2 interacts with gelsolin in osteoclasts, where PYK2 activation is required for the formation of actin rings. Together, our results suggest that PYK2 is a regulator of gelsolin, revealing a novel PYK2–gelsolin pathway in regulating actin cytoskeletal organization in multiple cells, including osteoclasts.

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Binding of Bruton's tyrosine kinase to Fyn, Lyn, or Hck through a Src homology 3 domain-mediated interaction.

Proceedings of the National Academy of Sciences ◽

10.1073/pnas.91.17.8152 ◽

1994 ◽

Vol 91 (17) ◽

pp. 8152-8155 ◽

Cited By ~ 104

Author(s):

G. Cheng ◽

Z. S. Ye ◽

D. Baltimore

Keyword(s):

Tyrosine Kinase ◽

Bruton’S Tyrosine Kinase ◽

Bruton's Tyrosine Kinase ◽

Src Homology 3 ◽

Src Homology 3 Domain ◽

Src Homology

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The activation mechanism of ACK1 (activated Cdc42-associated tyrosine kinase 1)

Biochemical Journal ◽

10.1042/bj20111575 ◽

2012 ◽

Vol 445 (2) ◽

pp. 255-264 ◽

Cited By ~ 19

Author(s):

Qiong Lin ◽

Jian Wang ◽

Chandra Childress ◽

Wannian Yang

Keyword(s):

Cell Adhesion ◽

Growth Factor ◽

Tyrosine Kinase ◽

Molecular Mechanism ◽

Growth Factor Receptor ◽

Activation Mechanism ◽

Src Homology 3 ◽

Src Homology 3 Domain ◽

Src Homology ◽

Epidermal Growth

ACK [activated Cdc42 (cell division cycle 42)-associated tyrosine kinase; also called TNK2 (tyrosine kinase, non-receptor, 2)] is activated in response to multiple cellular signals, including cell adhesion, growth factor receptors and heterotrimeric G-protein-coupled receptor signalling. However, the molecular mechanism underlying activation of ACK remains largely unclear. In the present study, we demonstrated that interaction of the SH3 (Src homology 3) domain with the EBD [EGFR (epidermal growth factor receptor)-binding domain] in ACK1 forms an auto-inhibition of the kinase activity. Release of this auto-inhibition is a key step for activation of ACK1. Mutation of the SH3 domain caused activation of ACK1, independent of cell adhesion, suggesting that cell adhesion-mediated activation of ACK1 is through releasing the auto-inhibition. A region at the N-terminus of ACK1 (Leu10–Leu14) is essential for cell adhesion-mediated activation. In the activation of ACK1 by EGFR signalling, Grb2 (growth-factor-receptor-bound protein 2) mediates the interaction of ACK1 with EGFR through binding to the EBD and activates ACK1 by releasing the auto-inhibition. Furthermore, we found that mutation of Ser445 to proline caused constitutive activation of ACK1. Taken together, our studies have revealed a novel molecular mechanism underlying activation of ACK1.

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