Serine/threonine-protein kinases SGK represent a kinase subfamily with orthologs found across animal

clades A clade (), also known as a monophyletic group or natural group, is a group of organisms that are monophyletic – that is, composed of a common ancestor and all its lineal descendants – on a phylogenetic tree. Rather than the English term, t ...

and in yeast (compar
Treefam family TF320906
. In most vertebrates, including humans, there are three isoforms encoded by the genes '' SGK1'', '' SGK2'', and ''

SGK3 Serine/threonine-protein kinase Sgk3 is an enzyme that in humans is encoded by the ''SGK3'' gene. Function This gene is a member of the serine/threonine protein kinase family and encodes a phosphoprotein with a PX (phox homology) domain. The ...

''. The name Serum/glucocorticoid-regulated kinase refers to the first cloning of a SGK family member from a cDNA library screen for genes upregulated by the glucocorticoid dexamethasone in a rat mammary epithelial tumor cell line. The first human family member (human '' SGK1'') was cloned in a screen of hepatocellular genes regulated in response to cellular hydration or swelling. The term SGK is also used as a synonym for '' SGK1''.

Function

Among the three SGK genes, the SGK1 gene is the most intensively studied. This gene encodes a serine/threonine protein kinase that is highly similar to the rat serum-and glucocorticoid-induced protein kinase (SGK). This gene was identified in a screen of hepatocellular genes regulated in response to cellular hydration or swelling. Cellular hydration is a

catabolic Catabolism () is the set of metabolic pathways that breaks down molecules into smaller units that are either oxidized to release energy or used in other anabolic reactions. Catabolism breaks down large molecules (such as polysaccharides, lipids, ...

signal, stimulating

glycogenolysis Glycogenolysis is the breakdown of glycogen (n) to glucose-1-phosphate and glycogen (n-1). Glycogen branches are catabolized by the sequential removal of glucose monomers via phosphorolysis, by the enzyme glycogen phosphorylase. Mechanism The ...

and

proteolysis Proteolysis is the breakdown of proteins into smaller polypeptides or amino acids. Uncatalysed, the hydrolysis of peptide bonds is extremely slow, taking hundreds of years. Proteolysis is typically catalysed by cellular enzymes called protease ...

, and inhibiting

protein Proteins are large biomolecules and macromolecules that comprise one or more long chains of amino acid residues. Proteins perform a vast array of functions within organisms, including catalysing metabolic reactions, DNA replication, respo ...

and

glycogen Glycogen is a multibranched polysaccharide of glucose that serves as a form of energy storage in animals, fungi, and bacteria. The polysaccharide structure represents the main storage form of glucose in the body. Glycogen functions as one o ...

synthesis. This kinase has been shown to be important in activating certain

potassium Potassium is the chemical element with the symbol K (from Neo-Latin ''kalium'') and atomic number19. Potassium is a silvery-white metal that is soft enough to be cut with a knife with little force. Potassium metal reacts rapidly with atmosphe ...

sodium Sodium is a chemical element with the symbol Na (from Latin ''natrium'') and atomic number 11. It is a soft, silvery-white, highly reactive metal. Sodium is an alkali metal, being in group 1 of the periodic table. Its only stable iso ...

, and chloride channels. Expression of this gene in hepatocytes is stimulated by transforming growth factor-beta ( TGF-beta), which participates in the pathophysiology of diabetic complications. Since both TGF-beta expression and SGK expression are elevated in diabetic nephropathy, an involvement of SGK in the development of this condition is suggested. The SGK1 kinase regulates the myo-inositol transporter during osmotic stress. Deregulated expression of SGK1 in the endometrium has been implicated in cases of

infertility Infertility is the inability of a person, animal or plant to reproduce by natural means. It is usually not the natural state of a healthy adult, except notably among certain eusocial species (mostly haplodiploid insects). It is the normal state ...

recurrent miscarriage Recurrent miscarriage is three or more consecutive pregnancy losses. In contrast, infertility is the inability to conceive. In many cases the cause of RPL is unknown. After three or more losses, a thorough evaluation is recommended by American So ...

in humans, and SGK1 expression in the

endometrium The endometrium is the inner epithelial layer, along with its mucous membrane, of the mammalian uterus. It has a basal layer and a functional layer: the basal layer contains stem cells which regenerate the functional layer. The functional laye ...

also affects fertility in mice.

References

{{Portal bar, Biology, border=no Human genes Human proteins EC 2.7.11