PIK3R1

Domain

The SH3 domain mediates the binding to CBLB, and to HIV-1 Nef.

Function

Binds to activated (phosphorylated) protein-Tyr kinases, through its SH2 domain, and acts as an adapter, mediating the association of the p110 catalytic unit to the plasma membrane. Necessary for the insulin-stimulated increase in glucose uptake and glycogen synthesis in insulin-sensitive tissues. Plays an important role in signaling in response to FGFR1, FGFR2, FGFR3, FGFR4, KITLG/SCF, KIT, PDGFRA and PDGFRB. Likewise, plays a role in ITGB2 signaling (PubMed:17626883, PubMed:19805105, PubMed:7518429). Modulates the cellular response to ER stress by promoting nuclear translocation of XBP1 isoform 2 in a ER stress- and/or insulin-dependent manner during metabolic overloading in the liver and hence plays a role in glucose tolerance improvement (PubMed:20348923).

Involvement in disease

Agammaglobulinemia 7, autosomal recessive

AGM7

A primary immunodeficiency characterized by profoundly low or absent serum antibodies and low or absent circulating B-cells due to an early block of B-cell development. Affected individuals develop severe infections in the first years of life.

None

The disease is caused by variants affecting the gene represented in this entry.

SHORT syndrome

SHORTS

A rare, multisystem disease characterized by short stature, anomalies of the anterior chamber of the eye, characteristic facial features such as triangular facies, lack of facial fat, and hypoplastic nasal alae with overhanging columella, partial lipodystrophy, hernias, hyperextensibility, and delayed dentition. The clinical phenotype can include insulin resistance, nephrocalcinosis, and hearing deficits. Developmental milestones and cognition are normal.

None

The disease is caused by variants affecting the gene represented in this entry.

Immunodeficiency 36 with lymphoproliferation

IMD36

A primary immunodeficiency characterized by impaired B-cell function, hypogammaglobulinemia and recurrent infections.

None

The disease is caused by variants affecting the gene represented in this entry.

Post-translational modifications

Polyubiquitinated in T-cells by CBLB; which does not promote proteasomal degradation but impairs association with CD28 and CD3Z upon T-cell activation.

In adipose tissue, polyubiquitinated by the BCR(KBTBD2) E3 ubiquitin ligase complex; recognized by KBTBD2 through the SH2 domains, undergoes 'Lys-48'-linked polyubiquitination leading to its degradation.

Phosphorylated. Tyrosine phosphorylated in response to signaling by FGFR1, FGFR2, FGFR3 and FGFR4. Phosphorylated by CSF1R. Phosphorylated by ERBB4. Phosphorylated on tyrosine residues by TEK/TIE2. Dephosphorylated by PTPRJ. Phosphorylated by PIK3CA at Ser-608; phosphorylation is stimulated by insulin and PDGF. The relevance of phosphorylation by PIK3CA is however unclear (By similarity). Phosphorylated in response to KIT and KITLG/SCF. Phosphorylated by FGR.

Sequence Similarities

Belongs to the PI3K p85 subunit family.

Tissue Specificity

Isoform 2 is expressed in skeletal muscle and brain, and at lower levels in kidney and cardiac muscle. Isoform 2 and isoform 4 are present in skeletal muscle (at protein level).

Alternative names

GRB1, PIK3R1, Phosphatidylinositol 3-kinase regulatory subunit alpha, PI3-kinase regulatory subunit alpha, PI3K regulatory subunit alpha, PtdIns-3-kinase regulatory subunit alpha, Phosphatidylinositol 3-kinase 85 kDa regulatory subunit alpha, PI3-kinase subunit p85-alpha, PtdIns-3-kinase regulatory subunit p85-alpha

Database links

swissprot:P27986 entrezGene:5296 entrezGene:5295 swissprot:O00459