Properties of highly viscous gels formed by neurofilaments in vitro. A possible consequence of a specific inter-filament cross-bridging.
Neurofilaments freshly isolated from bovine spinal cord form a reversible gel in vitro, consisting of nearly parallel and interlinked filaments organized in bundles. This phenomenon is obtained above a critical neurofilament concentration and is highly sensitive to denaturation. No gelation occurs with neurofilaments reconstituted from urea-solubilized subunits. The velocity of the gelation kinetics, optimum at a slightly acidic pH, is inhibited by low and high ionic strength and activated by millimolar concentrations of Mg2+ and other bivalent cations. No protein other than the purified neurofilament preparation itself (80-95% neurofilament triplet) is necessary for the formation of a gel. However, purified cytoskeletal proteins from microtubules and neurofilaments influence the viscosity of the native preparation. These observations suggest a reticulation in vitro between neurofilaments, dependent upon a fragile conformation of the polymers and possibly mediated through the high-Mr neurofilament subunits (200 kDa and 150 kDa). The significance of these results is discussed with regard to the inter-neurofilament cross-bridging in situ involving the 200 kDa subunit described by Hirokawa, Glicksman & Willard [(1984) J. Cell Biol. 98, 1523-1536].
Leterrier
J F
JF
Centre de Neurochimie du C.N.R.S., Strasbourg, France.
Eyer
J
J
D000818:Animals; D002417:Cattle; D003598:Cytoskeletal Proteins / Q000378:metabolism; D003599:Cytoskeleton / Q000378:metabolism*; D005782:Gels; D007382:Intermediate Filaments / Q000187:drug effects / Q000378:metabolism* / Q000648:ultrastructure; D007700:Kinetics; D046911:Macromolecular Substances; D008274:Magnesium / Q000494:pharmacology; D008854:Microscopy, Electron; D014783:Viscosity
D003598:Cytoskeletal Proteins; D005782:Gels; D046911:Macromolecular Substances; D008274:Magnesium