Ubiquitously expressed with high expression in fetal brain compared to adult brain. Abundant expression is observed in cerebellum, cerebral cortex, cerebral meninges, and vermis cerebelli.
Involvement in disease
Note=Defects in PIK3R5 may be a cause of autosomal recessive ataxia with oculomotor apraxia (AOA). A PIK3R5 mutation segregates with the disease phenotype in a family affected by gait ataxia, cerebellar dysarthric speech, and impaired ocular movement. Additional features include reduced or absent tendon reflexes, severe cerebellar atrophy, marked vermal atrophy, moderately severe axonal sensory polyneuropathy with absent sensory nerve action potential in the lower extremities, and persistently elevated alpha-fetoprotein levels.
The heterodimerization region allows the binding to the catalytic subunit.