Expression of CD47/integrin-associated protein induces death of cultured cerebral cortical neurons.

The death and survival of neuronal cells are regulated by various signaling pathways during development of the brain and in neuronal diseases. Previously, we demonstrated that the neuronal adhesion molecule brain immunoglobulin-like molecule with tyrosine-based activation motifs/SHP substrate 1 (BIT/SHPS-1) is involved in brain-derived neurotrophic factor (BDNF)-promoted neuronal cell survival. Here, we report the apoptosis-inducing effect of CD47/integrin-associated protein (IAP), the heterophilic binding partner of BIT/SHPS-1, on neuronal cells. We generated a recombinant adenovirus vector expressing a neuronal form of CD47/IAP, and found that the expression of CD47/IAP by infection with CD47/IAP adenovirus induced the death of cultured cerebral cortical neurons. The numbers of TdT-mediated biotin-dUTP nick-end labelling (TUNEL)-positive neurons and of cells displaying apoptotic nuclei increased by expression of CD47/IAP. Neuronal cell death was prevented by the addition of the broad-spectrum caspase inhibitor Z-VAD-fmk. Furthermore, we observed that co-expression of CD47/IAP with BIT/SHPS-1 enhanced neuronal cell death, and that BDNF prevented it. These results suggest that CD47/IAP is involved in a novel pathway which regulates caspase-dependent apoptosis of cultured cerebral cortical neurons. CD47/IAP-induced death of cultured cortical neurons may be regulated by the interaction of CD47/IAP with BIT/SHPS-1 and by BDNF.