Department of Neuroscience, Ohio State University, Columbus, OH 43210.
Center for Biostatistics and Department of Biomedical Informatics, Ohio State University, Columbus, OH 43210.
Mol Biol Cell. 2023 Jun 1;34(7):ar68. doi: 10.1091/mbc.E23-01-0024. Epub 2023 Mar 29.
Neurofilaments are cargoes of axonal transport which are unique among known intracellular cargoes in that they are long, flexible protein polymers. These polymers are transported into axons, where they accumulate in large numbers to drive the expansion of axon caliber, which is an important determinant of axonal conduction velocity. We reported previously that neurofilaments can be lengthened by joining ends, called end-to-end annealing, and that they can be shortened by severing. Here, we show that neurofilament annealing and severing are robust and quantifiable phenomena in cultured neurons that act antagonistically to regulate neurofilament length. We show that this in turn regulates neurofilament transport and that severing is regulated by N-terminal phosphorylation of the neurofilament subunit proteins. We propose that focal destabilization of intermediate filaments by site-directed phosphorylation may be a general enzymatic mechanism for severing these cytoskeletal polymers, providing a mechanism to regulate the transport and accumulation of neurofilaments in axons.
神经丝是轴突运输的载体，它们在已知的细胞内载体中是独一无二的，因为它们是长而灵活的蛋白质聚合物。这些聚合物被运输到轴突中，在那里它们大量积累，推动轴突口径的扩张，这是轴突传导速度的重要决定因素。我们之前报道过，神经丝可以通过连接末端（称为端到端退火）来延长，也可以通过切断来缩短。在这里，我们表明，神经丝退火和切断是培养神经元中强大且可量化的现象，它们拮抗作用以调节神经丝长度。我们表明，这反过来又调节神经丝运输，并且切断受神经丝亚基蛋白 N 端磷酸化的调节。我们提出，通过定点磷酸化使中间丝局部不稳定可能是切断这些细胞骨架聚合物的一般酶促机制，为调节神经丝在轴突中的运输和积累提供了一种机制。
