Oxidant stress-activated serine/threonine kinase that may play a role in the response to environmental stress. Targets to the Golgi apparatus where it appears to regulate protein transport events, cell adhesion, and polarity complexes important for cell migration.
The Golgi apparatus has long been suggested to be important for directing secretion to specific sites on the plasma membrane in response to extracellular signaling events. However, the mechanisms by which signaling events are coordinated with Golgi apparatus function remain poorly understood. Here, we identify a scaffolding function for the Golgi matrix protein GM130 that sheds light on how such signaling events may be regulated. We show that the mammalian Ste20 kinases YSK1 and MST4 target to the Golgi apparatus via the Golgi matrix protein GM130. In addition, GM130 binding activates these kinases by promoting autophosphorylation of a conserved threonine within the T-loop. Interference with YSK1 function perturbs perinuclear Golgi organization, cell migration, and invasion into type I collagen. A biochemical screen identifies 14-3-3zeta as a specific substrate for YSK1 that localizes to the Golgi apparatus, and potentially links YSK1 signaling at the Golgi apparatus with protein transport events, cell adhesion, and polarity complexes important for cell migration.
The Golgi apparatus has long been suggested to be important for directing secretion to specific sites on the plasma membrane in response to extracellular signaling events. However, the mechanisms by which signaling events are coordinated with Golgi apparatus function remain poorly understood. Here, we identify a scaffolding function for the Golgi matrix protein GM130 that sheds light on how such signaling events may be regulated. We show that the mammalian Ste20 kinases YSK1 and MST4 target to the Golgi apparatus via the Golgi matrix protein GM130. In addition, GM130 binding activates these kinases by promoting autophosphorylation of a conserved threonine within the T-loop. Interference with YSK1 function perturbs perinuclear Golgi organization, cell migration, and invasion into type I collagen. A biochemical screen identifies 14-3-3zeta as a specific substrate for YSK1 that localizes to the Golgi apparatus, and potentially links YSK1 signaling at the Golgi apparatus with protein transport events, cell adhesion, and polarity complexes important for cell migration.
Evidence
2:
Inferred from Physical InteractionIntAct
Individuals carrying a mutation in one of the three cerebral cavernous malformation genes (CCM1/KRIT1, CCM2, CCM3) cannot be clinically distinguished, raising the possibility that they act within common molecular pathways. In this study, we demonstrate that CCM3 (PDCD10) coprecipitates and colocalizes with CCM2. We also show that CCM3 directly binds to serine/threonine kinase 25 (STK25, YSK1, SOK1) and the phosphatase domain of Fas-associated phosphatase-1 (FAP-1, PTPN13, PTP-Bas, PTP-BL). CCM3 is phosphorylated by STK25 but not by its other Yeast-Two hybrid interactor STK24, whereas the C-terminal catalytic domain of FAP-1 dephosphorylates CCM3. Finally, our experiments reveal that STK25 forms a protein complex with CCM2. Thus, our data link two proteins of unknown function, CCM3 and STK25, with CCM2, which is part of signaling pathways essential for vascular development and CCM pathogenesis.
Interacting selectively and non-covalently with any protein or protein complex (a complex of two or more proteins that may include other nonprotein molecules).
Evidence
1:
Inferred from Physical InteractionIntAct
The Golgi apparatus has long been suggested to be important for directing secretion to specific sites on the plasma membrane in response to extracellular signaling events. However, the mechanisms by which signaling events are coordinated with Golgi apparatus function remain poorly understood. Here, we identify a scaffolding function for the Golgi matrix protein GM130 that sheds light on how such signaling events may be regulated. We show that the mammalian Ste20 kinases YSK1 and MST4 target to the Golgi apparatus via the Golgi matrix protein GM130. In addition, GM130 binding activates these kinases by promoting autophosphorylation of a conserved threonine within the T-loop. Interference with YSK1 function perturbs perinuclear Golgi organization, cell migration, and invasion into type I collagen. A biochemical screen identifies 14-3-3zeta as a specific substrate for YSK1 that localizes to the Golgi apparatus, and potentially links YSK1 signaling at the Golgi apparatus with protein transport events, cell adhesion, and polarity complexes important for cell migration.
Evidence
2:
Inferred from Physical InteractionIntAct
The serine/threonine protein phosphatases are targeted to specific subcellular locations and substrates in part via interactions with a wide variety of regulatory proteins. Understanding these interactions is thus critical to understanding phosphatase function. Using an iterative affinity purification/mass spectrometry approach, we generated a high density interaction map surrounding the protein phosphatase 2A catalytic subunit. This approach recapitulated the assembly of the PP2A catalytic subunit into many different trimeric complexes but also revealed several new protein-protein interactions. Here we define a novel large multiprotein assembly, referred to as the striatin-interacting phosphatase and kinase (STRIPAK) complex. STRIPAK contains the PP2A catalytic (PP2Ac) and scaffolding (PP2A A) subunits, the striatins (PP2A regulatory B''' subunits), the striatin-associated protein Mob3, the novel proteins STRIP1 and STRIP2 (formerly FAM40A and FAM40B), the cerebral cavernous malformation 3 (CCM3) protein, and members of the germinal center kinase III family of Ste20 kinases. Although the function of the CCM3 protein is unknown, the CCM3 gene is mutated in familial cerebral cavernous malformations, a condition associated with seizures and strokes. Our proteomics survey indicates that a large portion of the CCM3 protein resides within the STRIPAK complex, opening the way for further studies of CCM3 biology. The STRIPAK assembly establishes mutually exclusive interactions with either the CTTNBP2 proteins (which interact with the cytoskeletal protein cortactin) or a second subcomplex consisting of the sarcolemmal membrane-associated protein (SLMAP) and the related coiled-coil proteins suppressor of IKKepsilon (SIKE) and FGFR1OP2. We have thus identified several novel PP2A-containing protein complexes, including a large assembly linking kinases and phosphatases to a gene mutated in human disease.
Evidence
3:
Inferred from Physical InteractionIntAct
Systematic mapping of protein-protein interactions, or 'interactome' mapping, was initiated in model organisms, starting with defined biological processes and then expanding to the scale of the proteome. Although far from complete, such maps have revealed global topological and dynamic features of interactome networks that relate to known biological properties, suggesting that a human interactome map will provide insight into development and disease mechanisms at a systems level. Here we describe an initial version of a proteome-scale map of human binary protein-protein interactions. Using a stringent, high-throughput yeast two-hybrid system, we tested pairwise interactions among the products of approximately 8,100 currently available Gateway-cloned open reading frames and detected approximately 2,800 interactions. This data set, called CCSB-HI1, has a verification rate of approximately 78% as revealed by an independent co-affinity purification assay, and correlates significantly with other biological attributes. The CCSB-HI1 data set increases by approximately 70% the set of available binary interactions within the tested space and reveals more than 300 new connections to over 100 disease-associated proteins. This work represents an important step towards a systematic and comprehensive human interactome project.
Evidence
4:
Inferred from Physical InteractionIntAct
Individuals carrying a mutation in one of the three cerebral cavernous malformation genes (CCM1/KRIT1, CCM2, CCM3) cannot be clinically distinguished, raising the possibility that they act within common molecular pathways. In this study, we demonstrate that CCM3 (PDCD10) coprecipitates and colocalizes with CCM2. We also show that CCM3 directly binds to serine/threonine kinase 25 (STK25, YSK1, SOK1) and the phosphatase domain of Fas-associated phosphatase-1 (FAP-1, PTPN13, PTP-Bas, PTP-BL). CCM3 is phosphorylated by STK25 but not by its other Yeast-Two hybrid interactor STK24, whereas the C-terminal catalytic domain of FAP-1 dephosphorylates CCM3. Finally, our experiments reveal that STK25 forms a protein complex with CCM2. Thus, our data link two proteins of unknown function, CCM3 and STK25, with CCM2, which is part of signaling pathways essential for vascular development and CCM pathogenesis.
To clarify the upstream regulatory mechanism of mitogen-activated protein kinase (MAPK), we performed the reverse transcriptase-based polymerase chain reaction (RT-PCR) with degenerate primers synthesized based on sequences conserved among the kinase domains of yeast MAPK kinase kinases (MAPKKKs), Stell, Bck1, and Byr2. We isolated several mammalian cDNA fragments that encode kinase subdomains sharing significant sequence homology with yeast MAPKKKs. Subsequent screening of a HeLa cell cDNA library using one of these cDNA fragments as a probe resulted in the isolation of a full-length cDNA that encodes a novel protein kinase. The catalytic domain sequence of this gene product is closely related to those of budding yeast Sps1 and Ste20 protein kinases. Thus, we call this protein YSK1 (Yeast Sps1/Ste20-related Kinase 1). The transcript of YSK1 was detected in a wide range of tissues and cells. Immunoprecipitated YSK1 shows protein kinase activity. Although YSK1 is significantly similar in its kinase domain to kinases of the yeast and mammalian MAPK pathways, the overexpression of YSK1 did not lead to the activation of the ERK (extracellular signal-regulated kinase) pathway, JNK (c-Jun NH2-terminal kinase)/SAPK (stress-activated protein kinase) pathway, or p38/Mpk2 pathway. These results suggest that YSK1 may be involved in the regulation of a novel intracellular signaling pathway.
Any process that results in a change in state or activity of a cell or an organism (in terms of movement, secretion, enzyme production, gene expression, etc.) as a result of oxidative stress, a state often resulting from exposure to high levels of reactive oxygen species, e.g. superoxide anions, hydrogen peroxide (H2O2), and hydroxyl radicals.
Mammalian homologs of the yeast protein kinase, Sterile 20 (Ste20), can be divided into two groups based on their regulation and structure. The first group, which includes PAK1, is regulated by Rac and Cdc42Hs, and activators have been identified. In contrast, very little is known about activators, regulatory mechanisms or physiological roles of the other group, which consists of GC kinase and MST1. We have identified a human Ste20-like kinase from the GC kinase group, SOK-1 (Ste20/oxidant stress response kinase-1), which is activated by oxidant stress. The kinase is activated by autophosphorylation and is markedly inhibited by its non-catalytic C-terminal region. SOK-1 is activated 3- to 7-fold by reactive oxygen intermediates, but is not activated by growth factors, alkylating agents, cytokines or environmental stresses including heat shock and osmolar stress. Although these data place SOK-1 on a stress response pathway, SOK-1, unlike GC kinase and PAK1, does not activate either of the stress-activated MAP kinase cascades (p38 and SAPKs). SOK-1 is the first mammalian Ste20-like kinase which is activated by cellular stress, and the activation is relatively specific for oxidant stress. Since SOK-1 does not activate any of the known MAP kinase cascades, its activation defines a novel stress response pathway which is likely to include a unique stress-activated MAP kinase cascade.
The cellular process in which a signal is conveyed to trigger a change in the activity or state of a cell. Signal transduction begins with reception of a signal (e.g. a ligand binding to a receptor or receptor activation by a stimulus such as light), or for signal transduction in the absence of ligand, signal-withdrawal or the activity of a constitutively active receptor. Signal transduction ends with regulation of a downstream cellular process, e.g. regulation of transcription or regulation of a metabolic process. Signal transduction covers signaling from receptors located on the surface of the cell and signaling via molecules located within the cell. For signaling between cells, signal transduction is restricted to events at and within the receiving cell.
Mammalian homologs of the yeast protein kinase, Sterile 20 (Ste20), can be divided into two groups based on their regulation and structure. The first group, which includes PAK1, is regulated by Rac and Cdc42Hs, and activators have been identified. In contrast, very little is known about activators, regulatory mechanisms or physiological roles of the other group, which consists of GC kinase and MST1. We have identified a human Ste20-like kinase from the GC kinase group, SOK-1 (Ste20/oxidant stress response kinase-1), which is activated by oxidant stress. The kinase is activated by autophosphorylation and is markedly inhibited by its non-catalytic C-terminal region. SOK-1 is activated 3- to 7-fold by reactive oxygen intermediates, but is not activated by growth factors, alkylating agents, cytokines or environmental stresses including heat shock and osmolar stress. Although these data place SOK-1 on a stress response pathway, SOK-1, unlike GC kinase and PAK1, does not activate either of the stress-activated MAP kinase cascades (p38 and SAPKs). SOK-1 is the first mammalian Ste20-like kinase which is activated by cellular stress, and the activation is relatively specific for oxidant stress. Since SOK-1 does not activate any of the known MAP kinase cascades, its activation defines a novel stress response pathway which is likely to include a unique stress-activated MAP kinase cascade.
This protein acts as an enzyme. It is known to catalyze the following reaction
EC 2.7.11.1: ATP + a protein ⇄ ADP + a phosphoprotein.
CuratedUniProtKB
It requires the following cofactor
Magnesium.
CuratedUniProtKB
It is regulated in the following manner
Interaction with Golgi matrix protein GOLGA2 leads to autophosphorylation on Thr-174, possibly as a consequence of stabilization of dimer formation. The C-terminal non-catalytic region inhibits the kinase activity.
The Golgi apparatus has long been suggested to be important for directing secretion to specific sites on the plasma membrane in response to extracellular signaling events. However, the mechanisms by which signaling events are coordinated with Golgi apparatus function remain poorly understood. Here, we identify a scaffolding function for the Golgi matrix protein GM130 that sheds light on how such signaling events may be regulated. We show that the mammalian Ste20 kinases YSK1 and MST4 target to the Golgi apparatus via the Golgi matrix protein GM130. In addition, GM130 binding activates these kinases by promoting autophosphorylation of a conserved threonine within the T-loop. Interference with YSK1 function perturbs perinuclear Golgi organization, cell migration, and invasion into type I collagen. A biochemical screen identifies 14-3-3zeta as a specific substrate for YSK1 that localizes to the Golgi apparatus, and potentially links YSK1 signaling at the Golgi apparatus with protein transport events, cell adhesion, and polarity complexes important for cell migration.
Protein which catalyzes the phosphorylation of serine or threonine residues on target proteins by using ATP as phosphate donor. Such phosphorylation may cause changes in the function of the target protein. Protein kinases share a conserved catalytic core common to both serine/ threonine and tyrosine protein kinases.
A reference proteome is a set of protein sequences derived from a complete proteome which constitutes a defined standard for a particular user community. Reference proteomes are manually defined according to a number of criteria. They cover the proteomes of well- studied model organisms and other proteomes of interest for biomedical and biotechnological research. Reference proteomes have been selected to provide broad coverage of the tree of life, and constitute a representative cross-section of the taxonomic diversity to be found within UniProtKB.
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