Inverted Formin 2 Regulates Actin Dynamics by Antagonizing Rho/Diaphanous-related Formin Signaling

• Published in: Journal of the American Society of Nephrology Vol. 24; no. 6; pp. 917 - 929
• Main Authors: HUA SUN, SCHLONDORFF, Johannes, HIGGS, Henry N, POLLAK, Martin R
• Format: Journal Article
• Language: English
• Published: Washington, DC American Society of Nephrology 01.06.2013
• Subjects: Actins - metabolism; Basic Research; Biological and medical sciences; Carrier Proteins - metabolism; Cell Line, Transformed; Cytosol - metabolism; Dimerization; Glomerulosclerosis, Focal Segmental - genetics; Glomerulosclerosis, Focal Segmental - metabolism; Humans; Medical sciences; Membrane Microdomains - metabolism; Membrane Proteins - metabolism; Microfilament Proteins - chemistry; Microfilament Proteins - genetics; Microfilament Proteins - metabolism; Nephrology. Urinary tract diseases; Podocytes - cytology; Podocytes - metabolism; Point Mutation; Protein Structure, Quaternary; Protein Transport - physiology; Pseudopodia - metabolism; rhoA GTP-Binding Protein - metabolism; RNA, Small Interfering - metabolism; Signal Transduction - physiology; Signal transduction; Nephrology; Regulation(control); Actin; Dynamics; Contractile protein; Urology
• ISSN: 1046-6673; 1533-3450
• DOI: 10.1681/asn.2012080834

Mutations in inverted formin 2 INF2 are a common cause of familial FSGS. INF2 interacts with diaphanous-related formins (mDia) and antagonizes mDia-mediated actin polymerization in response to active Rho signaling, suggesting that dysregulation of these pathways may mediate the development of INF2-related FSGS. However, the precise mechanisms by which INF2 regulates actin-dependent podocyte behavior remain largely unknown. Here, we investigated the possible role of INF2 in both lamellipodia-associated actin dynamics and actin-dependent slit diaphragm (SD) protein trafficking by manipulating the expression of INF2 and the activity of Rho/mDia signaling in cultured podocytes. Activation of mDia in the absence of INF2 led to defective formation of lamellipodia and abnormal SD trafficking. Effects of mutations disrupting the INF2-mDia interaction suggested the specificity of the mDia-antagonizing effect of INF2 in maintaining the lamellipodium. Furthermore, we found that SD trafficking requires INF2 interaction with lipid raft components. In summary, INF2 regulates lamellipodial actin dynamics and the trafficking of slit diaphragm proteins by opposing Rho/mDia-mediated actin polymerization. Thus, in podocytes, INF2 appears to be an important modulator of actin-dependent behaviors that are under the control of Rho/mDia signaling.