Identification of erythrocyte p55/MPP1 as a binding partner of NF2 tumor suppressor protein/Merlin.

Neurofibromatosis type 2 is an inherited disorder characterized by the development of benign and malignant tumors on the auditory nerves and central nervous system with symptoms including hearing loss, poor balance, skin lesions, and cataracts. Here, we report a novel protein-protein interaction between NF2 protein (merlin or schwannomin) and erythrocyte p55, also designated as MPP1. The p55 is a conserved scaffolding protein with postulated functions in cell shape, hair cell development, and neural patterning of the retina. The FERM domain of NF2 protein binds directly to p55, and surface plasmon resonance analysis indicates a specific interaction with a kD value of 3.7 nM. We developed a specific monoclonal antibody against human erythrocyte p55, and found that both p55 and NF2 proteins are colocalized in the non-myelin-forming Schwann cells. This finding suggests that the p55-NF2 protein interaction may play a functional role in the regulation of apico-basal polarity and tumor suppression pathways in non-erythroid cells.