Phosphoinositide 3-kinase delta catalytic subunit (PI3Kδ (also known as p110δ))

Phosphoinositide 3-kinase delta catalytic subunit (PI3Kδ, p110δ) is an isoform of class I PI3K primarily expressed in leukocytes, where it plays a central role in cell signaling pathways critical for immune cell function. It is encoded by the PIK3CD gene, and acts as the catalytic subunit within the heterodimeric PI3Kδ enzyme complex, pairing with a p85-type regulatory subunit[5][4]. PI3Kδ phosphorylates the 3-hydroxyl position of the inositol ring in phosphatidylinositol (PI) lipids at cellular membranes, generating PIP3 and activating downstream effectors such as AKT/PKB, thereby modulating diverse biological processes including lymphocyte development, proliferation, differentiation, and survival[4][5][2]. Aberrant PI3Kδ activity is implicated in hematologic malignancies, immune deficiencies (notably Activated PI3K Delta Syndrome), autoimmunity, and inflammatory diseases, making it a key therapeutic target[8][4][5]. Several drugs targeting PI3Kδ are approved for certain lymphomas and leukemias, operating by enzyme inhibition to curb aberrant immune cell proliferation and survival, but pose safety challenges related to immune suppression and secondary complications[5][4][8].

Other names

p110 deltap110δPI3K deltaphosphatidylinositol-4,5-bisphosphate 3-kinase catalytic subunit delta isoformPIK3CD (gene symbol)phosphatidylinositol 3-kinase delta

Inhibition of the kinase activity of PI3Kδ, blocking phosphorylation of phosphatidylinositol substrates, modulation of downstream signaling such as AKT/mTOR pathway, inhibition of lymphocyte proliferation and survival