Effects of phosphorylation of the neurofilament L protein on filamentous structures.
Effects of phosphorylation of the neurofilament L protein (NF-L) on the reassembly system were studied by both sedimentation experiments and low-angle rotary shadowing. Bovine spinal cord NF-L was phosphorylated with 3-4 mol/mol protein by either the catalytic subunit of cAMP-dependent protein kinase or protein kinase C. Phosphorylated NF-L could not assemble into filaments. Phosphorylation by either cAMP-dependent protein kinase or protein kinase C inhibited the same step of the reassembly process. Phosphorylated NF-L remained as an 8-chain complex even in favorable conditions for reassembly. The extent of the effect of phosphorylation on the filamentous structure of NF-L was also investigated by using the catalytic subunit of cAMP-dependent protein kinase. The amount of unassembled NF-L increased linearly with increased phosphorylation in the sedimentation experiments. Structural observations indicated that 1 or 2 mol of phosphorylation is enough to inhibit reassembly and to induce disassembly, and the disassembly process was also observed. The filaments were shown to unravel with disassembly. Star-like clusters, which we reported as being the initial stage of reassembly, were also identified.
Hisanaga
S
S
Department of Anatomy and Cell Biology, Faculty of Medicine, University of Tokyo, Japan.
Gonda
Y
Y
Inagaki
M
M
Ikai
A
A
Hirokawa
N
N
D000818:Animals; D002417:Cattle; D007381:Intermediate Filament Proteins / Q000378:metabolism*; D007382:Intermediate Filaments / Q000378:metabolism*; D016900:Neurofilament Proteins; D010766:Phosphorylation; D011493:Protein Kinase C / Q000378:metabolism; D011494:Protein Kinases / Q000378:metabolism; D011499:Protein Processing, Post-Translational
D007381:Intermediate Filament Proteins; D016900:Neurofilament Proteins; C044882:neurofilament protein L; D011494:Protein Kinases; D011493:Protein Kinase C