PTPRN2

Receptor-type tyrosine-protein phosphatase N2 (R-PTP-N2) also known as islet cell autoantigen-related protein (ICAAR) and phogrin is an is_associated_with::enzyme that in humans is encoded by the PTPRN2 is_associated_with::gene. is_associated_with::PTPRN and PTPRN2 (this gene) are both found to be major is_associated_with::autoantigens associated with is_associated_with::insulin-dependent diabetes mellitus.

Function
Due to a close similarity in the gene sequences, the is_associated_with::protein encoded by this is_associated_with::gene has traditionally been considered a member of the is_associated_with::protein tyrosine phosphatase (PTP) family. PTPs are known to be is_associated_with::signaling molecules that regulate a variety of cellular processes including is_associated_with::cell growth, differentiation, mitotic cycle, and is_associated_with::oncogenic transformation. However, recent research has shown that the PTPRN2 mouse is_associated_with::homolog, known as phogrin, is_associated_with::phosphorylates the lipid is_associated_with::phosphatidylinositol rather than is_associated_with::tyrosine. Specifically, phogrin was shown to act upon is_associated_with::phosphatidylinositol 3-phosphate and is_associated_with::Phosphatidylinositol 4,5-diphosphate, whereas it has never been observed acting upon tyrosine. PTPRN2 should, therefore, be more accurately considered a PIPase rather than a PTPase. is_associated_with::Phosphorylated forms of is_associated_with::phosphatidylinositol (PI) are called is_associated_with::phosphoinositides and play important roles in is_associated_with::lipid signaling, is_associated_with::cell signaling and is_associated_with::membrane trafficking.

The protein produced by PTPRN2 possesses an is_associated_with::extracellular region, a single is_associated_with::transmembrane region, and a single is_associated_with::intracellular is_associated_with::catalytic domain, and thus represents a receptor-type PTP. The catalytic domain of this PTP is most closely related to is_associated_with::PTPRN, also known as IA-2.

Gene
Three is_associated_with::alternatively spliced is_associated_with::transcript variants of this gene, which encode distinct proteins, have been reported.

Interactions
PTPRN2 has been shown to interact with: is_associated_with::CKAP5, is_associated_with::SPTBN4, and is_associated_with::UBQLN4.

Clinical significance
R-PTP-N2 functions as an is_associated_with::autoantigen in is_associated_with::diabetes mellitus type 1.