The kinase SPE-55 promotes localized assembly of the major sperm protein in Caenorhabditis elegans spermatocytes
Published Web Location
https://www.nature.com/articles/s41467-026-77139-2
Abstract
The crawling motility of nematode sperm is driven by the unconventional cytoskeletal protein, Major Sperm Protein (MSP). In developing spermatocytes, MSP assembles on the cytosolic side of Golgi-derived membranous organelles (MOs) in structures called Fibrous Bodies (FBs). These MSP-laden FB-MO complexes facilitate the subsequent segregation of MSP to budding spermatids and away from central residual bodies. Here we identify SPE-55 as a key FB assembly factor. In spe-55 spermatocytes, MSP remains diffusely cytosolic, and minimal MSP segregates to spermatids. The resulting spe-55 spermatozoa are motility-defective. SPE-55 localizes directly to MOs where it recruits the intrinsically disordered protein SPE-18 to initiate FB assembly, yet unlike SPE-6 or SPE-18, SPE-55 is required neither to complete meiosis nor to produce spermatids. Our study reveals an essential interplay between localized kinases and intrinsically disordered proteins in assembling large cytoskeletal complexes.
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