The atypical Rho GTPase RhoU interacts with intersectin-2 to regulate endosomal recycling pathways

Abstract

Rho GTPases play a key role in various membrane trafficking processes. RhoU is an atypical small Rho GTPase related to Rac/Cdc42, which possesses unique N- and C-terminal domains that regulate its function and its subcellular localization. RhoU localizes at the plasma membrane, on endosomes and in cell adhesion structures where it governs cell signaling, differentiation and migration. However, despite its endomembrane localization, RhoU function in vesicular trafficking has been unexplored. Here, we identified intersectins (ITSNs) as new binding partners for RhoU and showed that the second PxxP motif at the N terminus of RhoU mediated interactions with the SH3 domains of ITSNs. To evaluate the function of RhoU and ITSNs in vesicular trafficking, we used fluorescent transferrin as a cargo for uptake experiments. We showed that silencing of either RhoU or ITSN2, but not ITSN1, increased transferrin accumulation in early endosomes, resulting from a defect in fast vesicle recycling. Concomitantly, RhoU and ITSN2 colocalized to a subset of Rab4-positive vesicles, suggesting that a RhoU–ITSN2 interaction may occur on fast recycling endosomes to regulate the fate of vesicular cargos.

LncRNA SNHG16 promotes development of oesophageal squamous cell carcinoma by interacting with EIF4A3 and modulating RhoU mRNA stability

“…The atypical Rho GTPase RhoU was originally isolated as a gene transcriptionally upregulated in wnt-1-transformed mouse mammary epithelial cells that shares distinct homology with Cdc42, as well as some biological functions [ 44 ]. For example, RhoU binds and activates p21-activated kinase (PAK1), induces filopodia and regulates cell tight junctions [ 45 ]. Impaired RhoU activity in fatty acid synthase-depleted cells leads to reduced adhesion turnover downstream of paxillin serine phosphorylation, which is rescued by the addition of exogenous palmitate [ 46 ].…”

“…Impaired RhoU activity in fatty acid synthase-depleted cells leads to reduced adhesion turnover downstream of paxillin serine phosphorylation, which is rescued by the addition of exogenous palmitate [ 46 ]. Previous studies reported that knockout of RhoU led to increased peripheral adhesions and reduced paxillin S272 phosphorylation, which is required for adhesion disassembly [ 45 ]. Upregulated RhoU in prostate cancer correlated with disease progression, and silencing of RhoU was shown to reduce the migratory ability of MDA-MB-231 and PC3 breast cancer cells [ 45 , 47 ].…”

“…Previous studies reported that knockout of RhoU led to increased peripheral adhesions and reduced paxillin S272 phosphorylation, which is required for adhesion disassembly [ 45 ]. Upregulated RhoU in prostate cancer correlated with disease progression, and silencing of RhoU was shown to reduce the migratory ability of MDA-MB-231 and PC3 breast cancer cells [ 45 , 47 ]. In our study, we found that EIF4A3 could interact with RhoU, and the enrichment of RhoU in anti-EIF4A3 precipitates was strengthened by SNHG16 overexpression.…”

Longitudinal variation of circulating Inc‐ITSN1‐2: A novel biomarker reflecting disease severity, inflammation, recurrence, and death risk in acute ischemic stroke patients

“…ITSNs have been recognized as crucial regulators in several cellular processes (such as membrane trafficking processes, cytoskeletal remodeling, transcription, translation, and metabolic processes). 21 , 22 , 23 For example, one previous study shows that ITSN‐1s dysregulation is responsible for pro‐inflammatory endothelial‐cell dysfunction induced by lipopolysaccharide. 21 Although sparse studies focus on Inc‐ITSN1‐2, its role in regulating inflammation has been noticed in several inflammatory disorders (including rheumatoid arthritis (RA), AS, SAP, and inflammatory bowel disease (IBD)).…”

“…ITSNs have been recognized as crucial regulators in several cellular processes (such as membrane trafficking processes, cytoskeletal remodeling, transcription, translation, and metabolic processes) 21–23 . For example, one previous study shows that ITSN‐1s dysregulation is responsible for pro‐inflammatory endothelial‐cell dysfunction induced by lipopolysaccharide 21 .…”