OBCAM, an immunoglobulin superfamily cell adhesion molecule, regulates morphology and proliferation of cerebral astrocytes

Abstract

Opioid-binding cell adhesion molecule (OBCAM) is a member of the immunoglobulin superfamily. In the present study, we investigated the expression and functional significance of OBCAM in cerebral astrocytes in vitro and in vivo. The confocal microscopic study revealed that the expression of OBCAM was prominent at filopodia and cellular processes of type-1 and -2 astrocytes. Moreover, the expression of OBCAM was shown to be stronger at the growth phase than the stationary one in type-1 ones. Ki-67-positive proliferating type-1 astrocytes showed higher frequency of OBCAM expression as compared with Ki-67-negative cells. The application of the anti-OBCAM IgG facilitated the proliferation of type-1 astrocytes at relatively low concentration (1 and 5 microg/mL) and had no effects at relatively high concentration (25 and 50 microg/mL). The cellular proliferation was not promoted when the anti-OBCAM Fab fragment was used, indicating that the antibody-induced clustering of OBCAM promotes the proliferation. The over-expression of OBCAM increased the cell size of type-1 astrocytes. Moreover, intense expression of OBCAM was observed on reactive astrocytes in the injured cerebrum in vivo. These results suggest that OBCAM is responsible for controlling the cell proliferation and growth in cortical astrocytes.