Effects of phosphorylation of the neurofilament L protein on filamentous structures

• Published in: Cell regulation Vol. 1; no. 2; pp. 237 - 248
• Main Authors: Hisanaga, S, Gonda, Y, Inagaki, M, Ikai, A, Hirokawa, N
• Format: Journal Article
• Language: English
• Published: United States 01-01-1990
• Subjects: Animals; Cattle; Intermediate Filament Proteins - metabolism; Intermediate Filaments - metabolism; Neurofilament Proteins; Phosphorylation; Protein Kinase C - metabolism; Protein Kinases - metabolism; Protein Processing, Post-Translational
• ISSN: 1044-2030
• DOI: 10.1091/mbc.1.2.237

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.