Normal Function
The PIK3CD gene provides instructions for making the p110 delta (p110δ) protein, which is one piece (subunit) of an enzyme called phosphatidylinositol 3-kinase (PI3K). The version of PI3K that contains the p110δ subunit, called PI3K delta, is found in white blood cells, including immune system cells (lymphocytes) called B cells and T cells. These cells recognize and attack foreign invaders, such as viruses and bacteria, to prevent infection.
PI3K delta functions as a kinase, which means that it adds a cluster of oxygen and phosphorus atoms (a phosphate group) to other proteins through a process called phosphorylation. PI3K delta phosphorylates certain signaling molecules, which triggers a series of additional reactions that transmit chemical signals within cells. In lymphocytes, PI3K delta signaling is important for many cell activities, including cell growth and division (proliferation) and maturation (differentiation). PI3K delta helps direct B cells and T cells to differentiate into different types, each of which has a distinct function in the immune system.
Health Conditions Related to Genetic Changes
Activated PI3K-delta syndrome
Variants (also called mutations) in the PIK3CD gene have been found to cause an immune disorder called activated PI3K-delta syndrome. PIK3CD gene variants cause a form of the condition called activated PI3K-delta syndrome type 1. People with activated PI3K-delta syndrome type 1 typically have recurrent bacterial infections of the respiratory tract and chronic viral infections.
The PIK3CD gene variants that cause activated PI3K-delta syndrome type 1 change single protein building blocks (amino acids) in the p110δ protein. These variants are classified as gain-of-function variants because a PI3K-delta enzyme that contains the altered subunit is frequently turned on (overactive). Studies indicate that this overactive signaling causes T cells to mature and die too quickly. The excess signaling also blocks maturation of B cells at an early stage; the immature B cells cannot respond to foreign invaders and likely self-destruct. The lack of T cells and B cells makes it difficult for people with this disorder to fight off bacterial and viral infections. Overactive of PI3K-delta signaling can also stimulate the abnormal proliferation of lymphocytes, and accumulation of these cells can lead to enlarged lymph nodes (lymphadenopathy). Activated PI3K-delta syndrome type 1 is also associated with an increased risk of developing a form of blood cell cancer called lymphoma.
More About This Health ConditionAutoimmune lymphoproliferative syndrome
MedlinePlus Genetics provides information about Autoimmune lymphoproliferative syndrome
More About This Health ConditionOther Names for This Gene
- p110D
- P110DELTA
- phosphatidylinositol-4,5-bisphosphate 3-kinase 110 kDa catalytic subunit delta
- phosphatidylinositol-4,5-bisphosphate 3-kinase, catalytic subunit delta
- phosphoinositide-3-kinase C
- PI3-kinase p110 subunit delta
Additional Information & Resources
Tests Listed in the Genetic Testing Registry
Scientific Articles on PubMed
Catalog of Genes and Diseases from OMIM
References
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