PTPRM - Homophilic Binding

Homophilic Binding

PTPmu protein expressed on the surface of cells is able to mediate binding between two cells, which results in the clustering of the cells, known as cell–cell aggregation. PTPmu accomplishes this by interacting with another PTPmu molecule on an adjacent cell, known as homophilic binding. The Ig domain of PTPmu is responsible for promoting homophilic binding. The Ig domain is also responsible for localizing PTPmu to the plasma membrane surface of the cell. The ability of closely related molecules like PTPmu and PTPkappa to separate themselves to associate only with their identically matched (homologous) molecules, known as sorting, is attributed to the MAM domain. The MAM, Ig, and the first two FNIII repeats are the minimum extracellular domains required for efficient cell–cell adhesion. Crystallographic studies demonstrated that the MAM and Ig domains are tightly associated into one functional entity. Additional crystal structure analysis by Aricescu and colleagues predicted that the adhesive interface between two PTPµ proteins is between the MAM and Ig domains of one PTPµ protein interacts with the first and second FN III domains of the second PTPµ protein. The type IIb RPTPs mediate adhesion, with the exception of PCP-2.