Phosphatidylinositol 3-kinase regulatory subunit alpha is an

enzyme An enzyme () is a protein that acts as a biological catalyst by accelerating chemical reactions. The molecules upon which enzymes may act are called substrate (chemistry), substrates, and the enzyme converts the substrates into different mol ...

that in humans is encoded by the ''PIK3R1''

gene In biology, the word gene has two meanings. The Mendelian gene is a basic unit of heredity. The molecular gene is a sequence of nucleotides in DNA that is transcribed to produce a functional RNA. There are two types of molecular genes: protei ...

Function

Phosphatidylinositol 3-kinase Phosphoinositide 3-kinases (PI3Ks), also called phosphatidylinositol 3-kinases, are a family of enzymes involved in cellular functions such as cell growth, proliferation, differentiation, motility, survival and intracellular trafficking, which i ...

phosphorylates the

inositol In biochemistry, medicine, and related sciences, inositol generally refers to ''myo''-inositol (formerly ''meso''-inositol), the most important stereoisomer of the chemical compound cyclohexane-1,2,3,4,5,6-hexol. Its elemental formula, formula is ...

ring of

phosphatidylinositol Phosphatidylinositol or inositol phospholipid is a biomolecule. It was initially called "inosite" when it was discovered by Léon Maquenne and Johann Joseph von Scherer in the late 19th century. It was discovered in bacteria but later also found ...

at the 3-prime position. The enzyme comprises a 110 kD catalytic subunit and a regulatory subunit of either 85, 55, or 50 kD. The ''Pik3r1'' gene locus encodes the 85 kD regulatory subunit, as well as 55 and 50 kD regulatory subunits. It used to be thought that alternative splicing of this gene resulted in three transcript variants encoding different isoforms. In fact, it has since been shown that the 55 and 50kD subunits have their own promotors within the gene locus ''Pik3r1''. Phosphatidylinositol 3-kinase plays an important role in the metabolic actions of

insulin Insulin (, from Latin ''insula'', 'island') is a peptide hormone produced by beta cells of the pancreatic islets encoded in humans by the insulin (''INS)'' gene. It is the main Anabolism, anabolic hormone of the body. It regulates the metabol ...

, and a mutation in this gene has been associated with

insulin resistance Insulin resistance (IR) is a pathological response in which cells in insulin-sensitive tissues in the body fail to respond normally to the hormone insulin or downregulate insulin receptors in response to hyperinsulinemia. Insulin is a horm ...

. Suppression specifically of the 85kD subunit in early murine embryoid body development results in a transient cell-cell adhesion deficiency, mediated by transient downregulation of the adhesion molecule integrin-beta1 (ITGB1).

Clinical significance

Mutations in ''PIK3R1'' are implicated in cases of

breast cancer Breast cancer is a cancer that develops from breast tissue. Signs of breast cancer may include a Breast lump, lump in the breast, a change in breast shape, dimpling of the skin, Milk-rejection sign, milk rejection, fluid coming from the nipp ...

. Mutations in PIK3R1 are associated to

SHORT syndrome SHORT syndrome is an uncommon autosomal-dominant condition marked by ocular depression, Rieger anomaly, teething delay, small height, hyperextensibility of joints, and/or hernias. It was characterized in 1975. Signs and symptoms The acronym SHO ...

Interactions

PIK3R1 has been shown to

interact Advocates for Informed Choice, dba interACT or interACT Advocates for Intersex Youth, is a 501(c)(3) nonprofit organization advocating for the legal and human rights of children with intersex traits. The organization was founded in 2006 and fo ...

with: *

ADAM12 Disintegrin and metalloproteinase domain-containing protein 12 (previously Meltrin) is an enzyme that in humans is encoded by the ''ADAM12'' gene. ADAM12 has two splice variants: ADAM12-L, the long form, has a transmembrane region and ADAM12-S, ...

, *

BCAR1 Breast cancer anti-estrogen resistance protein 1 is a protein that in humans is encoded by the ''BCAR1'' gene. Gene BCAR1 is localized on chromosome 16 on region q, on the negative strand and it consists of seven exons. Eight different gene i ...

, * CBLB, *

CD117 Proto-oncogene c-KIT is the gene encoding the receptor tyrosine kinase protein known as tyrosine-protein kinase KIT, CD117 ( cluster of differentiation 117) or mast/stem cell growth factor receptor (SCFR). Multiple transcript variants encoding d ...

, *

CD28 CD28 (Cluster of Differentiation 28) is a protein expressed on T cells that provides essential co-stimulation, co-stimulatory signals required for T cell activation and survival. When T cells are stimulated through CD28 in conjunction with the T- ...

, *

CD7 CD7 (Cluster of Differentiation 7) is a protein that in humans is encoded by the ''CD7'' gene. Function This gene encodes a transmembrane protein which is a member of the immunoglobulin superfamily. This protein is found on thymocytes and matu ...

, *

CENTG1 Arf-GAP with GTPase, ANK repeat and PH domain-containing protein 2 is a protein that in humans is encoded by the ''AGAP2'' gene. Interactions CENTG1 has been shown to interact with: * EPB41L1, * HOMER1 and * PIK3R1 Phosphatidylinositol 3- ...

, * CBL, *

EPHA2 EPH receptor A2 (ephrin type-A receptor 2) is a protein that in humans is encoded by the ''EPHA2'' gene. Function This gene belongs to the ephrin receptor subfamily of the protein-tyrosine kinase family. EPH and EPH-related receptors have be ...

, * EPOR, *

ERBB3 Receptor tyrosine-protein kinase erbB-3, also known as HER3 (human epidermal growth factor receptor 3), is a membrane bound protein that in humans is encoded by the ''ERBB3'' gene. ErbB3 is a member of the EGFR family, epidermal growth factor re ...

, * EZR, *

FCGR2A Low affinity immunoglobulin gamma Fc region receptor II-a is a protein that in humans is encoded by the ''FCGR2A'' gene. Interactions FCGR2A has been shown to interact with PIK3R1 and Syk. See also * CD32 CD32 (cluster of differentiation ...

, *

GAB1 GRB2-associated-binding protein 1 is a protein that in humans is encoded by the ''GAB1'' gene. Function The protein encoded by this gene is a member of the IRS1-like multisubstrate docking protein family. The encoded protein is an important ...

, *

GAB2 GRB2-associated-binding protein 2 also known as GAB2 is a protein that in humans is encoded by the ''GAB2'' gene. GAB2 is a docking protein with a conserved, folded PH domain attached to the membrane and a large disordered region, which hosts in ...

, *

Grb2 Growth factor receptor-bound protein 2, also known as Grb2, is an adaptor protein involved in signal transduction/ cell communication. In humans, the GRB2 protein is encoded by the ''GRB2'' gene. The protein encoded by this gene binds recepto ...

, *

HRAS GTPase HRas, from "Harvey Rat sarcoma virus", also known as transforming protein p21 is an enzyme that in humans is encoded by the gene. The ''HRAS'' gene is located on the short (p) arm of chromosome 11 (human), chromosome 11 at position 15.5, ...

, *

IRS1 Insulin receptor substrate 1 (IRS-1) is a signaling adapter protein that in humans is encoded by the ''IRS1'' gene. It is a 180 kDa protein with amino acid sequence of 1242 residues. It contains a single pleckstrin homology (PH) domain at the N-t ...

IRS2 Insulin receptor substrate 2 is a protein that in humans is encoded by the ''IRS2'' gene. Function This gene encodes the insulin receptor substrate 2, a cytoplasmic signaling molecule that mediates effects of insulin, insulin-like growth fact ...

, * IL1R1, *

JAK2 Janus kinase 2 (commonly called JAK2) is a non-receptor tyrosine kinase. It is a member of the Janus kinase family and has been implicated in signaling by members of the type II cytokine receptor family (e.g. interferon receptors), the GM-CSF ...

, *

KHDRBS1 KH domain-containing, RNA-binding, signal transduction-associated protein 1 is a protein that in humans is encoded by the ''KHDRBS1'' gene. This gene encodes a member of the KH domain, K homology domain-containing, RNA-binding, signal transductio ...

, * LTK, * LAT, * LCP2, * PIK3CD, *

PTK2 PTK2 protein tyrosine kinase 2 (PTK2), also known as focal adhesion kinase (FAK), is a protein that, in humans, is encoded by the ''PTK2'' gene. PTK2 is a focal adhesion-associated protein kinase involved in cellular adhesion (how cells stick to ...

, * SHB, *

TUBA1B Tubulin alpha-1B chain is a protein that in humans is encoded by the ''TUBA1B'' gene. Interactions TUBA1B has been shown to interact with PIK3R1 Phosphatidylinositol 3-kinase regulatory subunit alpha is an enzyme that in humans is encoded by ...

, * TYRO3, *

VAV1 Proto-oncogene vav is a protein that in humans is encoded by the ''VAV1'' gene. Function The protein encoded by this proto-oncogene is a member of the Dbl family of guanine nucleotide exchange factors (GEF) for the Rho family of GTP binding ...

, and * WAS.

Function

Clinical significance

Interactions

References

Further reading