– Phosphoinositide-3-kinase-interacting protein 1(PIK3IP1) is an enzyme that in humans is encoded by the PIK3IP1 gene.It is a negative regulator of phosphatidylinositol-3-kinase (PI3K), suppresses the development of hepatocellular carcinoma. The gene encoding PIK3IP1 maps to human chromosome 22, which houses over 500 genes and is the second smallest human chromosome. Mutations in several of the genes that map to chromosome 22 are involved in the development of Phelan-McDermid syndrome, Neurofibromatosis type 2, autism and schizophrenia.