Serine/threonine-protein kinases SGK represent a kinase subfamily with

orthologs Sequence homology is the biological homology between DNA, RNA, or protein sequences, defined in terms of shared ancestry in the evolutionary history of life. Two segments of DNA can have shared ancestry because of three phenomena: either a sp ...

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, ...

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

SGK1 Serine/threonine-protein kinase Sgk1 also known as serum and glucocorticoid-regulated kinase 1 is an enzyme that in humans is encoded by the SGK1 gene. SGK1 belongs to a subfamily of serine/threonine kinases that is under acute transcriptional co ...

'', ''

SGK2 Serine/threonine-protein kinase Sgk2 is an enzyme that in humans is encoded by the ''SGK2'' gene. This gene encodes a serine/threonine protein kinase. Although this gene product is similar to serum- and glucocorticoid-induced protein kinase (SGK ...

'', and '' SGK3''. 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 ''

'') 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 ''

''.

Function

Among the three SGK genes, the SGK1 gene is the most intensively studied. This gene encodes a

serine/threonine protein kinase A serine/threonine protein kinase () is a kinase enzyme, in particular a protein kinase, that phosphorylates the OH group of the amino-acid residues serine or threonine, which have similar side chains. At least 350 of the 500+ human prote ...

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, lipid ...

signal, stimulating glycogenolysis and proteolysis, 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, res ...

and glycogen 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 atmosph ...

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 ...

, and

chloride channels Chloride channels are a superfamily of poorly understood ion channels specific for chloride. These channels may conduct many different ions, but are named for chloride because its concentration ''in vivo'' is much higher than other anions. Several ...

. Expression of this gene in

hepatocytes A hepatocyte is a cell of the main parenchymal tissue of the liver. Hepatocytes make up 80% of the liver's mass. These cells are involved in: * Protein synthesis * Protein storage * Transformation of carbohydrates * Synthesis of cholesterol, ...

is stimulated by transforming growth factor-beta (

TGF-beta Transforming growth factor beta (TGF-β) is a multifunctional cytokine belonging to the transforming growth factor superfamily that includes three different mammalian isoforms (TGF-β 1 to 3, HGNC symbols TGFB1, TGFB2, TGFB3) and many other ...

), which participates in the pathophysiology of diabetic complications. Since both TGF-beta expression and SGK expression are elevated in

diabetic nephropathy Diabetic nephropathy, also known as diabetic kidney disease, is the chronic loss of kidney function occurring in those with diabetes mellitus. Diabetic nephropathy is the leading causes of chronic kidney disease (CKD) and end-stage renal disease ...

, an involvement of SGK in the development of this condition is suggested. The SGK1 kinase regulates the myo-inositol transporter during

osmotic stress Osmotic shock or osmotic stress is physiologic dysfunction caused by a sudden change in the solute concentration around a cell, which causes a rapid change in the movement of water across its cell membrane. Under hypertonic conditions - conditio ...

. Deregulated expression of SGK1 in the endometrium has been implicated in cases of infertility or

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 S ...

in humans, and SGK1 expression in the endometrium also affects fertility in mice.

References

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