Fast anterograde transport of membrane-bound organelles delivers molecules synthesized in the neuronal cell body outward to distant synapses. Identification of the molecular “zipcodes” on organelles that mediate attachment and activation of microtubule-based motors for this directed transport is a major area of inquiry. Here we identify a short peptide sequence (15 aa) from the cytoplasmic C terminus of amyloid precursor protein (APP-C) sufficient to mediate the anterograde transport of peptide-conjugated beads in the squid giant axon. APP-C beads travel at fast axonal transport rates (0.53 μm/s average velocity, 0.9 μm/s maximal velocity) whereas beads coupled to other peptides coinjected into the same axon remain stationary at the injection site. This transport appears physiologic, because it mimics behavior of endogenous squid organelles and of beads conjugated to C99, a polypeptide containing the full-length cytoplasmic domain of amyloid precursor protein (APP). Beads conjugated to APP lacking the APP-C domain are not transported. Coinjection of APP-C peptide reduces C99 bead motility by 75% and abolishes APP-C bead motility, suggesting that the soluble peptide competes with protein-conjugated beads for axoplasmic motor(s).

Seating Plan For Examination Download. The APP-C domain is conserved (13/15 aa) from squid to human, and peptides from either squid or human APP behave similarly. Thus, we have identified a conserved peptide zipcode sufficient to direct anterograde transport of exogenous cargo and suggest that one of APP's roles may be to recruit and activate axonal machinery for endogenous cargo transport.

Membrane-bound vesicles are primarily transported in neurons by fast axonal transport apparently on cytoskeletal tracks. Intracellular pathogens, such as herpes simplex virus (HSV), appear to coopt this cellular transport machinery (–) and thus may serve as tools to uncover the mechanisms governing cargo–motor interactions (, ). HSV, a neurotropic virus that causes the recurrent cold sore, travels back and forth within neuronal processes at different stages in its life cycle (). After the initial infection of the mucus membrane, HSV travels within the sensory nerve process to the trigeminal ganglion, where it enters latency. Upon reactivation, newly synthesized viral particles are packaged in the cell body and then travel out to the periphery by fast axonal transport within neuronal processes (–, –).

Download Pokemon Emerald Rtc Patch. Recently we reconstituted HSV transport in the giant axon of the squid in both directions [retrograde, as detergent-stripped particles (), and anterograde ()] by injecting GFP-labeled virus into the giant axon of the squid. Viral particles transported in the anterograde direction were associated with a high copy number (≈3,000 molecules per virion) of amyloid precursor protein (APP) (). Because APP has been implicated as a motor receptor for transport in other systems (–), we became interested in whether APP might play a role in anterograde transport of virus. In this study we focus on APP and its ability to drive transport by substituting polystyrene beads for virus and coating the beads with APP. If APP were sufficient to serve as a receptor for transport machinery, then APP should be able to mediate transport of exogenous cargo, such as polystyrene beads, in the giant axon.