SUBCELLULAR-DISTRIBUTION OF ALPHA-ACTININ IN CHICK BRAIN

To elucidate the possible involvement of brain alpha-actinin in neurot ransmission, we examined the subcellular distribution and content of c hick brain alpha-actinin. Different subfractions of chick brain tissue were isolated, including myelin, mitochondria, microsomes, cytoplasm, synaptosomes, and soluble synaptosomal proteins. The distribution and content of alpha-actinin were examined by immunoassay. Our results sh owed that only brain cytoplasm contained a detectable amount of alpha- actinin, and its level was 0.2% of total cytoplasmic proteins. The alp ha-actinin level in brain nerve endings was less than 0.1% of total sy naptosomal proteins. In addition, rat and horse brain synaptosomes wer e also examined by the same method and no alpha-actinin was detected. Our studies suggest that brain alpha-actinin is excluded from nerve en dings and is unlikely to be a regulatory protein involved in neurotran smission.