Cytoplasmic dynein conversion at a crush injury in rat peripheral axons

Cytoplasmic dynein is a motor for retrograde axonal transport for movement of membranous organelles toward the neuronal cell body, However, cytoplasmi c dynein is synthesized in the cell body and conveyed along the axon to ner ve terminals. To characterize the axonal transport of cytoplasmic dynein in relation to synaptic vesicles and other membrane compartments, immunocytoc hemical and cytofluorimetric scanning analyses of crush-operated rat sciati c nerves were performed. Distal to the crush, the kinetics of dynein accumu lation were consistent with its role in the retrograde transport of membran ous organelles. During the initial 3 hr after crush, only small amounts of dynein-immunoreactive material accumulated proximal to the crush. This is c onsistent with metabolic labeling studies showing that most of the dynein m oving in the anterograde direction is in the slow component of axonal trans port. Thereafter, the rate of proximal accumulation of dynein increased, an d by 8 hr postcrush a large amount of dynein immunoreactivity was observed. This accelerated accumulation may be due to recruitment of dynein from slo w component b onto organelles proximal to the crush. Double labeling demons trated that dynein immunoreactivity colocalized with synaptophysin, a trans membrane protein found in small, clear synaptic vesicles. In contrast, dyne in immunoreactivity did not colocalize well with calcitonin gene-related pe ptide (CGRP), a peptide matrix marker for some large dense-cored vesicles, Finally, dynein immunoreactivity colocalized with the anterograde transport motor kinesin both proximal and distal to a crush, suggesting that kinesin may carry some dynein-containing membrane compartments during fast anterog rade axonal transport, (C) 2000 Wiley-Liss, Inc.