The Mechanism for Regulation of the F-actin Binding Activity of IQGAP1 by Calcium/Calmodulin

Mateer, Scott C.; McDaniel, Amanda; Nicolas, Valérie; Habermacher, Geoffrey; Lin, Mei-Jung; Cromer, Damond A.; King, Michelle E.; Bloom, George S.

doi:10.1074/jbc.m109535200

Cited by 107 publications

(156 citation statements)

References 33 publications

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“…The finding that IQGAP1 redistribution is mimicked by PKC activation further suggests that IQGAP1 may be regulated not only by Ca 2ϩ /calmodulin (32) but also by PKC-dependent mechanisms. If, as proposed for NIH/3T3 cells (31), elevation of [Ca 2ϩ ] i reduces the interaction between IQGAP1 and actin filaments in gastric mucosal cells, this interaction could serve to release IQGAP1 from the cell cortex. Elevated Ca 2ϩ /calmodulin might exert a similar effect by suppressing the association between IQGAP1 and active Cdc42 (16,17,31).…”

Section: Discussionmentioning

confidence: 99%

“…If, as proposed for NIH/3T3 cells (31), elevation of [Ca 2ϩ ] i reduces the interaction between IQGAP1 and actin filaments in gastric mucosal cells, this interaction could serve to release IQGAP1 from the cell cortex. Elevated Ca 2ϩ /calmodulin might exert a similar effect by suppressing the association between IQGAP1 and active Cdc42 (16,17,31). This interaction could be further modulated by the activation of PKC and subsequent PKC-dependent phosphorylation of IQGAP1 or some associated regulatory protein.…”

Section: Discussionmentioning

confidence: 99%

“…Human IQGAP1 and IQGAP2 share 62% identity. IQGAP1 binds and cross-links actin filaments in vitro (1,12) and has been implicated in Ca 2ϩ /calmodulin signaling (16,31), Ecadherin-dependent cell adhesion (18,26,27,29), cell motility, and invasion (30,40) (see Refs. 4 and 32 for recent reviews).…”

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confidence: 99%

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IQGAPs are differentially expressed and regulated in polarized gastric epithelial cells

Chew

Okamoto²,

Chen³

et al. 2005

American Journal of Physiology-Gastrointestinal and Liver Physi

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. IQGAPs are differentially expressed and regulated in polarized gastric epithelial cells. Am J Physiol Gastrointest Liver Physiol 288: G376 -G387, 2005. First published September 30, 2004; doi:10.1152/ajpgi.00290.2004.-IQGAPs, GTPase-activating proteins with an IQ motif, are thought to regulate many actin cytoskeleton-based activities through interactions with Cdc42 and Rac. Recently, Cdc42 was implicated in regulation of gastric parietal cell HCl secretion, and IQGAP2 was immunolocalized with Cdc42 to F-actin-rich intracellular canalicular membranes of isolated gastric parietal cells in primary culture. Here we sought to define distribution and localization of IQGAP1 and IQGAP2 in major oxyntic (acid-secreting) gastric mucosal cell types and to determine whether secretory agonists modulate these proteins. Differential staining protocols were used to identify different cell populations (parietal, chief, surface/pit, and mucous neck cells) in semi-intact glands isolated from rabbit gastric mucosae and to characterize these same cells after dispersion and fractionation on isopycnic density gradients with simultaneous staining for F-actin, H ϩ -K ϩ -ATPase, and GSII lectinbinding sites. There was a pronounced increase in intracellular F-actin staining in dispersed chief cells, apparently from internalization of F-actin-rich apical membranes that normally abut the gland lumen. Therefore, other membrane-associated proteins might also be redistributed by disruption of cell-cell contacts. Western blot analyses were used to quantitate relative concentrations of IQGAPs in defined mucosal cell fractions, and gastric glands were used for in situ localizations. We detected uniform levels of IQGAP2 expression in oxyntic mucosal cells with predominant targeting to regions of cellcell contact and nuclei of all cell types. IQGAP2 was not detected in parietal cell intracellular canaliculi. IQGAP1 expression was variable and targeted predominantly to the cortex of chief and mucous neck cells. Parietal cells expressed little or no IQGAP1 vs. other mucosal cell types. Phosphoprotein affinity chromatography, isoelectric focusing, and phosphorylation site analyses indicated that both IQGAP1 and IQGAP2 are phosphoproteins potentially regulated by [Ca 2ϩ ]i/ PKC and cAMP signaling pathways, respectively. Stimulation of glands with carbachol, which elevates [Ca 2ϩ ]i and activates PKC, induced apparent translocation of IQGAP1, but not IQGAP2, to apical poles of chief (zymogen) and mucous neck cells. This response was mimicked by PMA but not by ionomycin or by elevation of [cAMP] i with forskolin. Our observations support a novel, PKC-dependent role for IQGAP1 in regulated exocytosis and suggest that IQGAP2 may play a more general role in regulating cell-cell interactions and possibly migration within the gastric mucosa. parietal cell; chief cell; protein kinase C; carbachol; actin THE RHO GTPASES Cdc42 and Rac1 regulate actin cytoskeletal dynamics by interacting with a number of effectors, including the IQGAPs (5, 15, 43), which are s...

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Section: Discussionmentioning

confidence: 99%

Section: Discussionmentioning

confidence: 99%

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IQGAPs are differentially expressed and regulated in polarized gastric epithelial cells

Chew

Okamoto²,

Chen³

et al. 2005

American Journal of Physiology-Gastrointestinal and Liver Physi

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“…IQGAP1 is an important regulator of the cytoskeleton [3]. IQGAP1 modulates actin function both by directly binding to F-actin [4,5] and indirectly via Cdc42 and Rac1 [6][7][8][9]. In addition, IQGAP1 appears to capture growing microtubule ends by binding CLIP-170 in a process regulated by Cdc42 and Rac1 [10].…”

Section: Introductionmentioning

confidence: 99%

Multiple proteins mediate IQGAP1-stimulated cell migration

Mataraza

Jeong

et al. 2007

Cellular Signalling

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Cell migration, a highly complex physiological phenomenon that requires the co-ordinated and tightly regulated function of several proteins, is mediated by a number of signalling pathways. Elucidation of the molecular mechanisms of cell migration impacts our comprehension of numerous cell functions, ranging from development and immune surveillance to angiogenesis and metastasis. The scaffold protein IQGAP1, which binds multiple proteins and regulates their functions, promotes cell motility. Many of the IQGAP1 binding proteins have been implicated in cell migration. In this study, we employed a multifaceted strategy to identify proteins that contribute to IQGAP1-stimulated cell migration. Using specific IQGAP1 point mutant constructs, an interaction with actin was shown to be essential for IQGAP1 to increase cell migration. In contrast, eliminating the binding of Ca 2+ / calmodulin, but not Ca 2+ -free calmodulin, augmented the ability of IQGAP1 to stimulate cell migration. Consistent with these findings, selective inhibition of calmodulin function at the plasma membrane with a specific peptide inhibitor enhanced cell migration mediated by IQGAP1. Interestingly, immunofluorescence staining and confocal microscopy suggest that localization of Cdc42 at the leading edge is not necessary for maximal migration of epithelial cells. Coupled with the observations that Cdc42 and Rac1 contribute to IQGAP1-stimulated cell migration, these data suggest that IQGAP1 serves as a junction to integrate multiple signalling molecules to facilitate cell migration.

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“…A moderate affinity of the actin-binding CHD (residues 1-210) has been measured in sedimentation assays (K d ϭ 47 M, 19). The affinity of full-length IQGAP1 for F-actin is higher, and can be estimated to the micromolar range, based on one data point (20). The structure of the CHD (residues 26 -210) has been solved by NMR (21).…”

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confidence: 99%

The IQGAP1 Protein Is a Calmodulin-regulated Barbed End Capper of Actin Filaments

Pelikan-Conchaudron¹,

Clainche

Didry

et al. 2011

Journal of Biological Chemistry

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IQGAP1 is a large modular protein that displays multiple partnership and is thought to act as a scaffold in coupling cell signaling to the actin and microtubule cytoskeletons in cell migration, adhesion, and cytokinesis. However the molecular mechanisms underlying the activities of IQGAP1 are poorly understood in part because of its large size, poor solubility and lack of functional assays to challenge biochemical properties in various contexts. We have purified bacterially expressed recombinant human IQGAP1. The protein binds Cdc42, Rac1, and the CRIB domain of N-WASP in a calmodulin-sensitive fashion. We further show that in addition to bundling of filaments via a single N-terminal calponin-homology domain, IQGAP1 actually regulates actin assembly. It caps barbed ends, with a higher affinity for ADP-bound terminal subunits (K B ‫؍‬ 4 nM). The barbed end capping activity is inhibited by calmodulin, consistent with calmodulin binding to IQGAP1 with a K C of 40 nM, both in the absence and presence of Ca 2؉ ions. The barbed end capping activity resides in the C-terminal half of IQGAP1. It is possible that the capping activity of IQGAP1 accounts for its stimulation of cell migration. We further find that bacterially expressed recombinant IQGAP1 fragments easily co-purify with nucleic acids that turn out to activate N-WASP protein to branch filaments with Arp2/3 complex. The present results open perspectives for tackling the function of IQGAP1 in more complex reconstituted systems.

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The Mechanism for Regulation of the F-actin Binding Activity of IQGAP1 by Calcium/Calmodulin

Cited by 107 publications

References 33 publications

IQGAPs are differentially expressed and regulated in polarized gastric epithelial cells

IQGAPs are differentially expressed and regulated in polarized gastric epithelial cells

Multiple proteins mediate IQGAP1-stimulated cell migration

The IQGAP1 Protein Is a Calmodulin-regulated Barbed End Capper of Actin Filaments

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