Phospholipase C-β1 Is Present in the Botrysome, an Intermediate Compartment-Like Organelle, and Is Regulated by Visual Experience in Cat Visual Cortex

Monoclonal antibody Cat-307 identifies a 165 kDa neuronal protein expressed in the cat visual cortex during the period of sensitivity to alterations in visual experience (Kind et al., 1994). Dark-rearing, which prolongs the sensitive period, also prolongs the expression of the Cat-307 protein. The Cat-307 protein localizes to an organelle, here called the botrysome (from the Greek botrys, cluster of grapes), that is located between the endoplasmic reticulum (ER) and Golgi apparatus. The botrysome is composed of small ring-shaped profiles with electron-dense coats. The size and morphology of the rings and their coats are similar to those described for ER to Golgi transport vesicles. Biochemically, the Cat-307 protein cofractionates with microsomes and partitions with subunits of the coatomerproteins that coat ER-to-Golgi transport vesicles. Partial amino acid sequencing reveals that the Cat-307 protein is phospholipase C-β1, the G-protein-dependent phosphodiesterase that hydrolyses phosphatidylinositol 4,5 biphosphate into inositol 1,4,5 triphosphate and diacylglycerol after the stimulation of a variety of neurotransmitter receptors at the cell surface. These results suggest a role for phospholipase C-β1 and the botrysome in developmental plasticity and provide a possible link between receptor activation at the cell surface and protein transport during neuronal development.