Neurobeachin: A protein kinase A-anchoring, beige/Chediak-Higashi protein homolog implicated in neuronal membrane traffic

We describe the identification and initial characterization of neurobeachin , a neuron-specific multidomain protein of 327 kDa with a high-affinity bin ding site (K-d,10 nM) for the type II regulatory subunit of protein kinase A (PKA RII). Neurobeachin is peripherally associated with pleomorphic tubul ovesicular endomembranes near the trans sides of Golgi stacks and throughou t the cell body and cell processes. It is also found in a subpopulation of synapses, where it is concentrated at the postsynaptic plasma membrane. In live cells, perinuclear neurobeachin is dispersed by brefeldin A (BFA) with in 1 min, and in permeabilized cells a recruitment of neurobeachin from cyt osol to Golgi-near membranes is stimulated by GTP gammaS and prevented by b refeldin A. Spots of neurobeachin recruitment are close to but distinct fro m recruitment sites of COP-I, AP-1, and AP-3 coat proteins involved in vesi cle budding. These observations indicate that neurobeachin binding to membr anes close to the trans-Golgi requires an ADP-ribosylation factor-like GTPa se, possibly in association with a novel type of protein coat. A neurobeach in isoform that does not bind RII, beige-like protein (BGL), is expressed i n many tissues. Neurobeachin, BGL, and similar to 10 other mammalian gene p roducts share a characteristic C-terminal BEACH-WD40 sequence module, which is also present in gene products of invertebrates, plants, protozoans, and yeasts, thus defining a new protein family. The prototype member of this f amily of BEACH domain proteins, lysosomal trafficking regulator (LYST), is deficient in genetic defects of protein sorting in lysosome biogenesis (the beige mouse and Chediak-Higashi syndrome). Neurobeachin's subcellular loca lization, its coat protein-like membrane recruitment, and its sequence simi larity to LYST suggest an involvement in neuronal post-Golgi membrane traff ic, one of its functions being to recruit protein kinase A to the membranes with which it associates.