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Mechanism of multi-site phosphorylation from a ROCK-I:RhoE complex structure.

ABSTRACT: The ROCK-I serine/threonine protein kinase mediates the effects of RhoA to promote the formation of actin stress fibres and integrin-based focal adhesions. ROCK-I phosphorylates the unconventional G-protein RhoE on multiple N- and C-terminal sites. These phosphorylation events stabilise RhoE, which functions to antagonise RhoA-induced stress fibre assembly. Here, we provide a molecular explanation for multi-site phosphorylation of RhoE from the crystal structure of RhoE in complex with the ROCK-I kinase domain. RhoE interacts with the C-lobe alphaG helix of ROCK-I by means of a novel binding site remote from its effector region, positioning its N and C termini proximal to the ROCK-I catalytic site. Disruption of the ROCK-I:RhoE interface abolishes RhoE phosphorylation, but has no effect on the ability of RhoE to disassemble stress fibres. In contrast, mutation of the RhoE effector region attenuates RhoE-mediated disruption of the actin cytoskeleton, indicating that RhoE exerts its inhibitory effects on ROCK-I through protein(s) binding to its effector region. We propose that ROCK-I phosphorylation of RhoE forms part of a feedback loop to regulate RhoA signalling.

SUBMITTER: Komander D

PROVIDER: S-EPMC2579254 | biostudies-literature |

REPOSITORIES: biostudies-literature

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RhoE function is regulated by ROCK I-mediated phosphorylation.

Project description:The Rho GTPase family member RhoE regulates actin filaments partly by binding to and inhibiting ROCK I, a serine/threonine kinase that induces actomyosin contractility. Here, we show that ROCK I can phosphorylate multiple residues on RhoE in vitro. In cells, ROCK I-phosphorylated RhoE localizes in the cytosol, whereas unphosphorylated RhoE is primarily associated with membranes. Phosphorylation has no effect on RhoE binding to ROCK I, but instead increases RhoE protein stability. Using phospho-specific antibodies, we show that ROCK phosphorylates endogenous RhoE at serine 11 upon cell stimulation with platelet-derived growth factor, and that this phosphorylation requires an active protein kinase C signalling pathway. In addition, we demonstrate that phosphorylation of RhoE correlates with its activity in inducing stress fibre disruption and inhibiting Ras-induced transformation. This is the first demonstration of an endogenous Rho family member being phosphorylated in vivo and indicates that phosphorylation is an important mechanism to control the stability and function of this GTPase-deficient Rho protein.

| S-EPMC556412 | biostudies-other

Mixed mechanisms of multi-site phosphorylation.

Project description:Multi-site phosphorylation is ubiquitous in cell biology and has been widely studied experimentally and theoretically. The underlying chemical modification mechanisms are typically assumed to be distributive or processive. In this paper, we study the behaviour of mixed mechanisms that can arise either because phosphorylation and dephosphorylation involve different mechanisms or because phosphorylation and/or dephosphorylation can occur through a combination of mechanisms. We examine a hierarchy of models to assess chemical information processing through different mixed mechanisms, using simulations, bifurcation analysis and analytical work. We demonstrate how mixed mechanisms can show important and unintuitive differences from pure distributive and processive mechanisms, in some cases resulting in monostable behaviour with simple dose-response behaviour, while in other cases generating new behaviour-like oscillations. Our results also suggest patterns of information processing that are relevant as the number of modification sites increases. Overall, our work creates a framework to examine information processing arising from complexities of multi-site modification mechanisms and their impact on signal transduction.

| S-EPMC4590494 | biostudies-literature

Reduced expression of RhoE promotes ROCK-dependent invasion in transformed human fibroblasts

Project description:Cen3tel cells, obtained by telomerase immortalization of human fibroblasts, gradually underwent neoplastic transformation and became metastatic in immunocompromised mice. Neoplastic transformation was associated with a change in cell morphology (from fibroblastic to polygonal). Tumorigenic cells acquired a clear-cut membrane localization of adhesion molecules, a reorganization of the actin cytoskeleton, increased cell motility and invasiveness. In a 3-dimensional environment, tumorigenic cells showed a spherical morphology with cortical actin rings, suggesting a switch from a mesenchymal to an amoeboid ROCK-dependent movement. Accordingly, cell invasion decreased upon treatment with the ROCK inhibitor Y27632, but not with the matrix protease inhibitor Ro28-2653. The increased invasiveness of tumorigenic cen3tel cells was associated with a reduced expression of RhoE, a cellular inhibitor of ROCK. Ectopic RhoE expression decreased cen3tel invasion capability. These results point to RhoE and ROCK as regulators of invasiveness of mesenchymal tumor cells and indicate ROCK as a possible therapeutic target. The cen3tel telomerase immortalized cell line was obtained from primary cen3 fibroblasts, derived from a centenarian individual, by infection with an hTERT-containing retrovirus (Mondello et al., 2003). Cen3tel cells were used at different steps of propagation, reflecting different phases of transformation (Zongaro et al., 2005) to study variations in the migratory and invasive potential accompanying human fibroblast neoplastic transformation. Raw data files: *NORM.txt test is Cy5 and *DS.txt test is Cy3.

2011-04-20 | E-GEOD-15742 | biostudies-arrayexpress

The RhoE/ROCK/ARHGAP25 signaling pathway controls cell invasion by inhibition of Rac activity.

Project description:Rhabdomyosarcoma (RMS) is the most common soft tissue sarcoma of skeletal muscle origin in children and adolescents. Among RMS subtypes, alveolar rhabdomyosarcoma (ARMS), which is characterized by the presence of the PAX3-FOXO1A or PAX7-FOXO1A chimeric oncogenic transcription factor, is associated with poor prognosis and a strong risk of metastasis compared with the embryonal subtype (ERMS). To identify molecular pathways involved in ARMS aggressiveness, we first characterized the migratory behavior of cell lines derived from ARMS and ERMS biopsies using a three-dimensional spheroid cell invasion assay. ARMS cells were more invasive than ERMS cells and adopted an ellipsoidal morphology to efficiently invade the extracellular matrix. Moreover, the invasive potential of ARMS cells depended on ROCK activity, which is regulated by the GTPase RhoE. Specifically, RhoE expression was low in ARMS biopsies, and its overexpression in ARMS cells reduced their invasion potential. Conversely, ARHGAP25, a GTPase-activating protein for Rac, was up-regulated in ARMS biopsies. Moreover, we found that ARHGAP25 inhibits Rac activity downstream of ROCKII and is required for ARMS cell invasion. Our results indicate that the RhoE/ROCK/ARHGAP25 signaling pathway promotes ARMS invasive potential and identify these proteins as potential therapeutic targets for ARMS treatment.

| S-EPMC5007086 | biostudies-literature

Reduced expression of RhoE promotes ROCK-dependent invasion in transformed human fibroblasts

2011-04-20 | GSE15742 | GEO

Multi-site Neurogenin3 Phosphorylation Controls Pancreatic Endocrine Differentiation.

Project description:The proneural transcription factor Neurogenin3 (Ngn3) plays a critical role in pancreatic endocrine cell differentiation, although regulation of Ngn3 protein is largely unexplored. Here we demonstrate that Ngn3 protein undergoes cyclin-dependent kinase (Cdk)-mediated phosphorylation on multiple serine-proline sites. Replacing wild-type protein with a phosphomutant form of Ngn3 increases α cell generation, the earliest endocrine cell type to be formed in the developing pancreas. Moreover, un(der)phosphorylated Ngn3 maintains insulin expression in adult β cells in the presence of elevated c-Myc and enhances endocrine specification during ductal reprogramming. Mechanistically, preventing multi-site phosphorylation enhances both Ngn3 stability and DNA binding, promoting the increased expression of target genes that drive differentiation. Therefore, multi-site phosphorylation of Ngn3 controls its ability to promote pancreatic endocrine differentiation and to maintain β cell function in the presence of pro-proliferation cues and could be manipulated to promote and maintain endocrine differentiation in vitro and in vivo.

| S-EPMC5425251 | biostudies-literature

Differentiation of opioid drug effects by hierarchical multi-site phosphorylation.

Project description:Differences in the ability of opioid drugs to promote regulated endocytosis of ?-opioid receptors are related to their tendency to produce drug tolerance and dependence. Here we show that drug-specific differences in receptor internalization are determined by a conserved, 10-residue sequence in the receptor's carboxyl-terminal cytoplasmic tail. Diverse opioids induce receptor phosphorylation at serine (S)375, present in the middle of this sequence, but opioids differ markedly in their ability to drive higher-order phosphorylation on flanking residues [threonine (T)370, T376, and T379]. Multi-phosphorylation is required for the endocytosis-promoting activity of this sequence and occurs both sequentially and hierarchically, with S375 representing the initiating site. Higher-order phosphorylation involving T370, T376, and T379 specifically requires GRK2/3 isoforms, and the same sequence controls opioid receptor internalization in neurons. These results reveal a biochemical mechanism differentiating the endocytic activity of opioid drugs.

| S-EPMC3583494 | biostudies-literature

Multi-site

Project description:Highly competitive fungi manipulate bacterial communities in decomposing wood

| PRJEB22364 | ENA

RhoE is a pro-survival p53 target gene that inhibits ROCK I-mediated apoptosis in response to genotoxic stress.

Project description:The Rho family of GTPases regulates many aspects of cellular behavior through alterations to the actin cytoskeleton . The majority of the Rho family proteins function as molecular switches cycling between the active, GTP-bound and the inactive, GDP-bound conformations . Unlike typical Rho-family proteins, the Rnd subfamily members, including Rnd1, Rnd2, RhoE (also known as Rnd3), and RhoH, are GTPase deficient and are thus expected to be constitutively active . Here, we identify an unexpected role for RhoE/Rnd3 in the regulation of the p53-mediated stress response. We show that RhoE is a transcriptional p53 target gene and that genotoxic stress triggers actin depolymerization, resulting in actin-stress-fiber disassembly through p53-dependent RhoE induction. Silencing of RhoE induction in response to genotoxic stress maintains stress fiber formation and strikingly increases apoptosis, implying an antagonistic role for RhoE in p53-dependent apoptosis. We found that RhoE inhibits ROCK I (Rho-associated kinase I) activity during genotoxic stress and thereby suppresses apoptosis. We demonstrate that the p53-mediated induction of RhoE in response to DNA damage favors cell survival partly through inhibition of ROCK I-mediated apoptosis. Thus, RhoE is anticipated to function by regulating ROCK I signaling to control the balance between cell survival and cell death in response to genotoxic stress.

| S-EPMC2779528 | biostudies-literature

Multi-site phosphorylation controls the neurogenic and myogenic activity of E47.

Project description:The superfamily of basic-Helix-Loop-Helix (bHLH) transcription factors influence cell fate in all three embryonic germ layers, and the tissue-specific class II factors have received prominent attention for their potent ability to direct differentiation during development and in cellular reprogramming. The activity of many class II bHLH proteins driving differentiation, and the inhibitory class VI bHLH factor Hes1, is controlled by phosphorylation on multiple sites by Cyclin-dependent kinases (Cdks). As class II proteins are generally thought to be active through hetero-dimerisation with the ubiquitously expressed class I E proteins, regulation of class I transcription factors such as E47 may influence the activity of multiple tissue-specific bHLH proteins. Using differentiation of nerve and muscle in Xenopus frog embryos as a model system, we set out to explore whether with the ubiquitously expressed class I E protein E47 that hetero-dimerises with Class II bHLHs to control their activity, is also regulated by multi-site phosphorylation. We demonstrate that E47 can be readily phosphorylated by Cdks on multiple sites in vitro, while ectopically-expressed E47 exists in multiple phosphorylated forms in Xenopus embryos. Preventing multi-site phosphorylation using a phospho-mutant version of E47 enhances the neurogenic and myogenic activity of three different class II bHLH reprogramming factors, and also when E47 acts in hetero-dimerisation with endogenous proteins. Mechanistically, unlike phospho-regulation of class II bHLH factors, we find that preventing phosphorylation of E47 increases the amount of chromatin-bound E47 protein but without affecting its overall protein stability. Thus, multi-site phosphorylation is a conserved regulatory mechanism across the bHLH superfamily that can be manipulated to enhance cellular differentiation.

| S-EPMC6405440 | biostudies-literature

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