During the fiscal year we accomplished the following: 1. Hepatocyte growth factor (HGF) attenuates agonist-induced endothelial cell (EC) permeability and increases pulmonary endothelial barrier function via Rac-dependent enhancement of the peripheral actin cytoskeleton. We showed that HGF both induced co-localization of IQGAP1 with Asef (a Rac/Cdc42-specific guanine nucleotide exchange factor) at the cell cortex and stimulated formation of an Asef-IQGAP1 functional protein complex. Asef knockdown attenuated HGF-induced Rac activation and Rac association with IQGAP1, and it abolished both IQGAP1 accumulation at the cell cortical layer and IQGAP1 interaction with actin cytoskeletal regulators cortactin and Arp3. Silencing IQGAP1 attenuated HGF-induced enhancement of EC barrier. These results demonstrate a novel feedback mechanism of HGF-induced endothelial barrier enhancement via Asef/IQGAP1 interactions, which regulate the level of HGF-induced Rac activation and promote cortical cytoskeletal remodeling via IQGAP1- Arp3/cortactin interactions. 2. Tight junction (TJ) formation, which contributes to cell-cell adhesion of polarized epithelia, is crucial for tissue homeostasis. The junctional complex is compromised in several pathological states, including carcinoma, inflammatory bowel disease and diabetic retinopathy. We observed that silencing IQGAP1 in kidney cells enhanced a transient increase in transepithelial electrical resistance. Analysis by quantitative microscopy and biochemical assays suggested that the effect of IQGAP1 is mediated by reduced expression and recruitment of claudin 2, and increased TJ recruitment of claudin 4. In addition, IQGAP1 knockdown increases the activity of the Cdc42 effector JNK (c-Jun N-terminal kinase). These data reveal that IQGAP1 modulates TJ formation by both controlling the recruitment of claudin 2 and claudin 4 to the TJ and by transient inhibition of the Cdc42-JNK pathway.

Agency
National Institute of Health (NIH)
Institute
Clinical Center (CLC)
Type
Investigator-Initiated Intramural Research Projects (ZIA)
Project #
1ZIACL080017-05
Application #
9154136
Study Section
Project Start
Project End
Budget Start
Budget End
Support Year
5
Fiscal Year
2015
Total Cost
Indirect Cost
Name
Clinical Center
Department
Type
DUNS #
City
State
Country
Zip Code
Ozdemir, E Sila; Jang, Hyunbum; Gursoy, Attila et al. (2018) Unraveling the molecular mechanism of interactions of the Rho GTPases Cdc42 and Rac1 with the scaffolding protein IQGAP2. J Biol Chem 293:3685-3699
Zhang, Mingzhen; Li, Zhigang; Wang, Guanqiao et al. (2018) Calmodulin (CaM) Activates PI3K? by Targeting the ""Soft"" CaM-Binding Motifs in Both the nSH2 and cSH2 Domains of p85?. J Phys Chem B :
Alves, Gelio; Wang, Guanghui; Ogurtsov, Aleksey Y et al. (2018) Rapid Classification and Identification of Multiple Microorganisms with Accurate Statistical Significance via High-Resolution Tandem Mass Spectrometry. J Am Soc Mass Spectrom 29:1721-1737
Li, Zhigang; Zhang, Yonghong; Hedman, Andrew C et al. (2017) Calmodulin Lobes Facilitate Dimerization and Activation of Estrogen Receptor-?. J Biol Chem 292:4614-4622
Chawla, Bhavna; Hedman, Andrew C; Sayedyahossein, Samar et al. (2017) Absence of IQGAP1 Protein Leads to Insulin Resistance. J Biol Chem 292:3273-3289
Bessède, Emilie; Molina, Silvia; Acuña-Amador, Luis et al. (2016) Deletion of IQGAP1 promotes Helicobacter pylori-induced gastric dysplasia in mice and acquisition of cancer stem cell properties in vitro. Oncotarget 7:80688-80699
Byrnes, Colleen; Lee, Y Terry; Meier, Emily R et al. (2016) Iron dose-dependent differentiation and enucleation of human erythroblasts in serum-free medium. J Tissue Eng Regen Med 10:E84-9
LeCour Jr, Louis; Boyapati, Vamsi K; Liu, Jing et al. (2016) The Structural Basis for Cdc42-Induced Dimerization of IQGAPs. Structure 24:1499-508
Sayedyahossein, Samar; Li, Zhigang; Hedman, Andrew C et al. (2016) IQGAP1 Binds To YAP and Modulates Its Transcriptional Activity. J Biol Chem :
Choi, Suyong; Hedman, Andrew C; Sayedyahossein, Samar et al. (2016) Agonist-stimulated phosphatidylinositol-3,4,5-trisphosphate generation by scaffolded phosphoinositide kinases. Nat Cell Biol 18:1324-1335

Showing the most recent 10 out of 34 publications