PTCH 2 ( patched homolog 2 ( Drosophila ) )

Receptor of Hedgehog ligands but lacks the strong capacity of PTCH1 to inhibit the signaling molecule Smoothened, which, through a series of intracellular events, activates the GLI family of transcription factors. Thus, while PTCH1 regulates Smoothened activity depending on Hedgehog ligand binding, PTCH2 is not. This is despite the fact that the three mammalian Hedgehog ligands Sonic, Desert and Indian Hedgehog have similar affinity for both PTCH1 and PTCH2. The expression of the PTCH2 receptor and the Desert Hedgehog ligand in the testis, as well as the requirement of Desert Hedgehog in testicular development has led to the proposal that PTCH2 may mediate the Desert Hedgehog effects in that tissue and could act as a tumor suppressor in germ cell tumors, as these are frequently deleted in 1p33-34. However, no PTCH2 mutations have been identified in such tumors and knock-out mouse models of PTCH2 have not revealed any testicular phenotype.