Protocadherin

Protocadherins were discovered by Shintaro Suzuki's group, when they used PCR to find new members of the cadherin family. The PCR fragments that corresponded to Protocadherins were found in vertebrate and invertebrate species. This wide range suggested that the fragments were part of an ancient cadherin and were thus termed "Protocadherins" as the "first cadherins".

It turns out that protocadherins are the largest subfamily of cadherins present in mammals as differentiators of specific cells. Their function has also been linked to homophilic adhesion, and the protocadherins have been identified as mediators of this adhesion. However, further evidence suggests that protocadherins can also act as signaling or receptor molecules.