Aplysia ror forms clusters on the surface of identified neuroendocrine cells

The ror receptors are a highly conserved family of receptor tyrosine kinase s genetically implicated in the establishment of cellular polarity, We have cloned a ror receptor from the marine mollusk Aplysia californica, Aplysia ror (Apror) is expressed in most developing neurons and some adult neurona l populations, including the neuroendocrine bag-cell neurons. The Apror pro tein is present in peripheral neuronal processes and ganglionic neuropil, i mplicating the kinase in the regulation of growth and/or synaptic events. I n cultured bag-cell neurons, the majority of the protein is stored in intra cellular organelles, whereas only a small fraction is expressed on the surf ace, When expressed on the cell surface, the protein is clustered on neurit es, suggesting that Apror is involved in the organization of functional dom ains within neurons. Apror immunoreactivity partially colocalizes with the P-type calcium channel BC-alpha 1A at bag-cell neuron varicosities, suggest ing a role for Apror in organizing neuropeptide release sites.