SGK1 Recombinant Protein

This gene encodes a serine/threonine protein kinase that plays an important role in cellular stress response. This kinase activates certain potassium, sodium, and chloride channels, suggesting an involvement in the regulation of processes such as cell survival, neuronal excitability, and renal sodium excretion. High levels of expression of this gene may contribute to conditions such as hypertension and diabetic nephropathy. Several alternatively spliced transcript variants encoding different isoforms have been noted for this gene. [provided by RefSeq, Jan 2009]

Function: Serine/threonine-protein kinase which is involved in the regulation of a wide variety of ion channels, membrane transporters, cellular enzymes, transcription factors, neuronal excitability, cell growth, proliferation, survival, migration and apoptosis. Plays an important role in cellular stress response. Contributes to regulation of renal Na+ retention, renal K+ elimination, salt appetite, gastric acid secretion, intestinal Na+/H+ exchange and nutrient transport, insulin-dependent salt sensitivity of blood pressure, salt sensitivity of peripheral glucose uptake, cardiac repolarization and memory consolidation. Up-regulates Na+ channels: SCNN1A/ENAC, SCN5A and ASIC1/ACCN2, K+ channels: KCNJ1/ROMK1, KCNA1-5, KCNQ1-5 and KCNE1, epithelial Ca2+ channels: TRPV5 and TRPV6, chloride channels: BSND, CLCN2 and CFTR, glutamate transporters: SLC1A3/EAAT1, SLC1A2 /EAAT2, SLC1A1/EAAT3, SLC1A6/EAAT4 and SLC1A7/EAAT5, amino acid transporters: SLC1A5/ASCT2, SLC38A1/SN1 and SLC6A19, creatine transporter: SLC6A8, Na+/dicarboxylate cotransporter: SLC13A2/NADC1, Na+-dependent phosphate cotransporter: SLC34A2/NAPI-2B, glutamate receptor: GRIK2/GLUR6. Up-regulates carriers: SLC9A3/NHE3, SLC12A1/NKCC2, SLC12A3/NCC, SLC5A3/SMIT, SLC2A1/GLUT1, SLC5A1/SGLT1 and SLC15A2/PEPT2. Regulates enzymes: GSK3A/B, PMM2 and Na+/K+ ATPase, and transcription factors: CTNNB1 and nuclear factor NF-kappa-B. Stimulates sodium transport into epithelial cells by enhancing the stability and expression of SCNN1A/ENAC. This is achieved by phosphorylating the NEDD4L ubiquitin E3 ligase, promoting its interaction with 14-3-3 proteins, thereby preventing it from binding to SCNN1A/ENAC and targeting it for degradation. Regulates store-operated Ca(+2) entry (SOCE) by stimulating ORAI1 and STIM1. Regulates KCNJ1/ROMK1 directly via its phosphorylation or indirectly via increased interaction with SLC9A3R2/NHERF2. Phosphorylates MDM2 and activates MDM2-dependent ubiquitination of p53/TP53. Phosphorylates MAPT/TAU and mediates microtubule depolymerization and neurite formation in hippocampal neurons. Phosphorylates SLC2A4/GLUT4 and up-regulates its activity. Phosphorylates APBB1/FE65 and promotes its localization to the nucleus. Phosphorylates MAPK1/ERK2 and activates it by enhancing its interaction with MAP2K1/MEK1 and MAP2K2/MEK2. Phosphorylates FBXW7 and plays an inhibitory role in the NOTCH1 signaling. Phosphorylates FOXO1 resulting in its relocalization from the nucleus to the cytoplasm. Phosphorylates FOXO3, promoting its exit from the nucleus and interference with FOXO3-dependent transcription. Phosphorylates BRAF and MAP3K3/MEKK3 and inhibits their activity. Phosphorylates SLC9A3/NHE3 in response to dexamethasone, resulting in its activation and increased localization at the cell membrane. Phosphorylates CREB1. Necessary for vascular remodeling during angiogenesis. Sustained high levels and activity may contribute to conditions such as hypertension and diabetic nephropathy. Isoform 2 exhibited a greater effect on cell plasma membrane expression of SCNN1A/ENAC and Na+ transport than isoform 1. Ref.3 Ref.15 Ref.16 Ref.17 Ref.18 Ref.19 Ref.20 Ref.21 Ref.22 Ref.23 Ref.25 Ref.26 Ref.27 Ref.28 Ref.29 Ref.30 Ref.31 Ref.32 Ref.33 Ref.34 Ref.35 Ref.36 Ref.38 Ref.39 Ref.41 Ref.42 Ref.43 Ref.48 Ref.49 Ref.51 Ref.53 Ref.55

Catalytic activity: ATP + a protein = ADP + a phosphoprotein.

Enzyme regulation: Two specific sites, one in the kinase domain (Thr-256) and the other in the C-terminal regulatory region (Ser-422), need to be phosphorylated for its full activation. Phosphorylation at Ser-397 and Ser-401 are also essential for its activity. Activated by WNK1, WNK2, WNK3 and WNK4.

Subunit structure: Homodimer; disulfide-linked. Forms a trimeric complex with FBXW7 and NOTCH1. Interacts with MAPK3/ERK1, MAPK1/ERK2, MAP2K1/MEK1, MAP2K2/MEK2, NEDD4, NEDD4L, MAPT/TAU, MAPK7, CREB1, SLC9A3R2/NHERF2 and KCNJ1/ROMK1. Associates with the mammalian target of rapamycin complex 2 (mTORC2) via an interaction with MAPKAP1/SIN1. Ref.13 Ref.17 Ref.20 Ref.36 Ref.39 Ref.48 Ref.52 Ref.60

Subcellular location: Cytoplasm. Nucleus. Endoplasmic reticulum membrane. Cell membrane Ref.3 Ref.40 Ref.55. Mitochondrion. Note: The subcellular localization is controlled by the cell cycle, as well as by exposure to specific hormones and environmental stress stimuli. In proliferating cells, it shuttles between the nucleus and cytoplasm in synchrony with the cell cycle, and in serum/growth factor-stimulated cells it resides in the nucleus. In contrast, after exposure to environmental stress or treatment with glucocorticoids, it is detected in the cytoplasm and with certain stress conditions is associated with the mitochondria. In osmoregulation through the epithelial sodium channel, it can be localized to the cytoplasmic surface of the cell membrane. Nuclear, upon phosphorylation. Ref.3 Ref.40 Ref.55Isoform 2: Cell membrane Ref.3 Ref.40 Ref.55.

Tissue specificity: Expressed in most tissues with highest levels in the pancreas, followed by placenta, kidney and lung. Isoform 2 is strongly expressed in brain and pancreas, weaker in heart, placenta, lung, liver and skeletal muscle. Ref.3 Ref.10

Induction: Induced by a very large spectrum of stimuli distinct from glucocorticoids and serum. These include aldosterone, cell shrinkage, cell swelling, TGF-beta, ischemic injury of the brain, neuronal excitotoxicity memory consolidation, chronic viral hepatitis, DNA-damaging agents, vitamin D3 psychophysiological stress, iron, glucose, EDN1, CSF2, fibroblast growth factor, platelet-derived growth factor, phorbolesters, follicle-stimulating hormone, sorbitol, heat shock, oxidative stress, UV irradiation, and p53/TP53. Many of these stimuli are highly cell-specific, as is the case, for example for aldosterone, which has been found to stimulate its expression only in cells derived from aldosterone-responsive epithelia. Isoform 2 is not induced by glucocorticoids but by excessive extracellular glucose and by TGFB1, in cultured cells. Ref.3

Domain: Isoform 2 subcellular localization at the cell membrane and resistance to proteasomal degradation is mediated by the sequences within the first 120 amino acids.

Post-translational modification: Regulated by phosphorylation. Activated by phosphorylation on Ser-422 by mTORC2, transforming it into a substrate for PDPK1 which phosphorylates it on Thr-256. Phosphorylation on Ser-397 and Ser-401 are also essential for its activity. Phosphorylation on Ser-78 by MAPK7 is required for growth factor-induced cell cycle progression.Ubiquitinated by NEDD4L; which promotes proteasomal degradation. Ubiquitinated by SYVN1 at the endoplasmic reticulum; which promotes rapid proteasomal degradation and maintains a high turnover rate in resting cells. Isoform 2 shows enhanced stability. Ref.37

Sequence similarities: Belongs to the protein kinase superfamily. AGC Ser/Thr protein kinase family.Contains 1 AGC-kinase C-terminal domain.Contains 1 protein kinase domain.