Slow axonal transport of the cytosolic chaperonin CCT with Hsc73 and actin in motor neurons

Molecular chaperones are well known for their role in facilitating the folding of nascent and newly synthesized proteins, but have other roles, including the assembly, translocation and renaturation of intracellular proteins: Axons are convenient tissues for the study of some of these other roles because they lack the capacity for significant protein synthesis. We examine the axonal transport of the cytosolic chaperonin containing T-complex polypeptide 1 (CCT) by labeling lumbar motor neurons with [S-35]methionine and examining sciatic nerve proteins by 2-D gel electrophoresis and immuno blotting. All CCT subunits identifiable with specific antibodies, namely CCTalpha, CCTbeta, CCTgamma and CCTepsilon/CCTtheta (the latter two subunits colocalized in analyses of rat nerve samples), appeared to be labeled in "slow component b" of axonal transport along with the molecular chaperone Hsc73 and actin, a major folding substrate for CCT. Our results are consistent with molecular chaperones having a post-translational role in maintaining the native form of actin during its slow transport to the axon terminal and ensuring its correct assembly into microfilaments. (C) 2002 Wiley-Liss, Inc.