GIT1 Activates p21-Activated Kinase through a Mechanism Independent of p21 Binding

ABSTRACT p21-activated kinases (PAKs) associate with a guanine nucleotide exchange factor, Pak-interacting exchange factor (PIX), which in turn binds the paxillin-associated adaptor GIT1 that targets the complex to focal adhesions. Here, a detailed structure-function analysis of GIT1 reveals how this multidomain adaptor also participates in activation of PAK. Kinase activation does not occur via Cdc42 or Rac1 GTPase binding to PAK. The ability of GIT1 to stimulate αPAK autophosphorylation requires the participation of the GIT N-terminal Arf-GAP domain but not Arf-GAP activity and involves phosphorylation of PAK at residues common to Cdc42-mediated activation. Thus, the activation of PAK at adhesion complexes involves a complex interplay between the kinase, Rho GTPases and protein partners that provide localization cues.

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Cloning and Characterization of GEF-H1, a Microtubule-associated Guanine Nucleotide Exchange Factor for Rac and Rho GTPases

Journal of Biological Chemistry ◽

10.1074/jbc.273.52.34954 ◽

1998 ◽

Vol 273 (52) ◽

pp. 34954-34960 ◽

Cited By ~ 210

Author(s):

Yong Ren ◽

Rong Li ◽

Yi Zheng ◽

Harris Busch

Keyword(s):

Rho Gtpases ◽

Guanine Nucleotide Exchange Factor ◽

Guanine Nucleotide ◽

Nucleotide Exchange ◽

Exchange Factor ◽

Guanine Nucleotide Exchange ◽

Nucleotide Exchange Factor

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Gef1p, a New Guanine Nucleotide Exchange Factor for Cdc42p, Regulates Polarity inSchizosaccharomyces pombe

Molecular Biology of the Cell ◽

10.1091/mbc.e02-07-0400 ◽

2003 ◽

Vol 14 (1) ◽

pp. 313-323 ◽

Cited By ~ 62

Author(s):

Pedro M. Coll ◽

Yadira Trillo ◽

Amagoia Ametzazurra ◽

Pilar Perez

Keyword(s):

Cell Morphology ◽

Rho Gtpases ◽

Genetic Interaction ◽

Guanine Nucleotide Exchange Factor ◽

Guanine Nucleotide ◽

Nucleotide Exchange ◽

Exchange Factor ◽

Guanine Nucleotide Exchange ◽

Nucleotide Exchange Factor

Schizosaccharomyces pombe cdc42+regulates cell morphology and polarization of the actin cytoskeleton. Scd1p/Ral1p is the only described guanine nucleotide exchange factor (GEF) for Cdc42p in S. pombe. We have identified a new GEF, named Gef1p, specifically regulating Cdc42p. Gef1p binds to inactive Cdc42p but not to other Rho GTPases in two-hybrid assays. Overexpression of gef1+increases specifically the GTP-bound Cdc42p, and Gef1p is capable of stimulating guanine nucleotide exchange of Cdc42p in vitro. Overexpression ofgef1+causes changes in cell morphology similar to those caused by overexpression of the constitutively active cdc42G12V allele. Gef1p localizes to the septum. gef1+deletion is viable but causes a mild cell elongation and defects in bipolar growth and septum formation, suggesting a role for Gef1p in the control of cell polarity and cytokinesis. The double mutant gef1Δ scd1Δ is not viable, indicating that they share an essential function as Cdc42p activators. However, both deletion and overexpression of either gef1+orscd1+causes different morphological phenotypes, which suggest different functions. Genetic evidence revealed a link between Gef1p and the signaling pathway of Shk1/Orb2p and Orb6p. In contrast, no genetic interaction between Gef1p and Shk2p-Mkh1p pathway was observed.

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Increased Expression of Ect2, a Guanine Nucleotide Exchange Factor for Rho GTPases, in Hyperplastic Alveolar Epithelial Cells in IPF

Pneumologie ◽

10.1055/s-0029-1202439 ◽

2009 ◽

Vol 63 (02) ◽

Author(s):

M Königshoff ◽

S Becker ◽

O Eickelberg

Keyword(s):

Epithelial Cells ◽

Rho Gtpases ◽

Guanine Nucleotide Exchange Factor ◽

Alveolar Epithelial Cells ◽

Guanine Nucleotide ◽

Nucleotide Exchange ◽

Exchange Factor ◽

Alveolar Epithelial ◽

Guanine Nucleotide Exchange ◽

Nucleotide Exchange Factor

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Crystal structure of a guanine nucleotide exchange factor encoded by the scrub typhus pathogenOrientia tsutsugamushi

Proceedings of the National Academy of Sciences ◽

10.1073/pnas.2018163117 ◽

2020 ◽

Vol 117 (48) ◽

pp. 30380-30390

Author(s):

Christopher Lim ◽

Jason M. Berk ◽

Alyssa Blaise ◽

Josie Bircher ◽

Anthony J. Koleske ◽

...

Keyword(s):

Rho Gtpases ◽

Sequence Similarity ◽

Ectopic Expression ◽

Guanine Nucleotide Exchange Factor ◽

Guanine Nucleotide ◽

Nucleotide Exchange ◽

Exchange Factor ◽

Guanine Nucleotide Exchange ◽

Nucleotide Exchange Factor

Rho family GTPases regulate an array of cellular processes and are often modulated by pathogens to promote infection. Here, we identify a cryptic guanine nucleotide exchange factor (GEF) domain in the OtDUB protein encoded by the pathogenic bacteriumOrientia tsutsugamushi. A proteomics-based OtDUB interaction screen identified numerous potential host interactors, including the Rho GTPases Rac1 and Cdc42. We discovered a domain in OtDUB with Rac1/Cdc42 GEF activity (OtDUBGEF), with higher activity toward Rac1 in vitro. While this GEF bears no obvious sequence similarity to known GEFs, crystal structures of OtDUBGEFalone (3.0 Å) and complexed with Rac1 (1.7 Å) reveal striking convergent evolution, with a unique topology, on a V-shaped bacterial GEF fold shared with other bacterial GEF domains. Structure-guided mutational analyses identified residues critical for activity and a mechanism for nucleotide displacement. Ectopic expression of OtDUB activates Rac1 preferentially in cells, and expression of the OtDUBGEFalone alters cell morphology. Cumulatively, this work reveals a bacterial GEF within the multifunctional OtDUB that co-opts host Rac1 signaling to induce changes in cytoskeletal structure.

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