The two C. elegans class VI myosins, SPE-15/HUM-3 and HUM-8, share similar motor properties, but have distinct developmental and tissue expression patterns

Ranya Behbehani; Chloe Johnson; Alexander J Holmes; Matthew J Gratian; Daniel P Mulvihill; Folma Buss

doi:10.3389/fphys.2024.1368054

The two C. elegans class VI myosins, SPE-15/HUM-3 and HUM-8, share similar motor properties, but have distinct developmental and tissue expression patterns

Front Physiol. 2024 Apr 10:15:1368054. doi: 10.3389/fphys.2024.1368054. eCollection 2024.

Authors

Ranya Behbehani¹, Chloe Johnson¹, Alexander J Holmes¹, Matthew J Gratian¹, Daniel P Mulvihill², Folma Buss¹

Affiliations

¹ Cambridge Institute for Medical Research, University of Cambridge, Cambridge, United Kingdom.
² School of Biosciences, University of Kent, Canterbury, United Kingdom.

Abstract

Myosins of class VI move toward the minus-end of actin filaments and play vital roles in cellular processes such as endocytosis, autophagy, protein secretion, and the regulation of actin filament dynamics. In contrast to the majority of metazoan organisms examined to date which contain a single MYO6 gene, C. elegans, possesses two MYO6 homologues, SPE-15/HUM-3 and HUM-8. Through a combination of in vitro biochemical/biophysical analysis and cellular assays, we confirmed that both SPE-15/HUM-3 and HUM-8 exhibit reverse directionality, velocities, and ATPase activity similar to human MYO6. Our characterization also revealed that unlike SPE-15/HUM-3, HUM-8 is expressed as two distinct splice isoforms, one with an additional unique 14 amino acid insert in the cargo-binding domain. While lipid and adaptor binding sites are conserved in SPE-15/HUM-3 and HUM-8, this conservation does not enable recruitment to endosomes in mammalian cells. Finally, we performed super-resolution confocal imaging on transgenic worms expressing either mNeonGreen SPE-15/HUM-3 or wrmScarlet HUM-8. Our results show a clear distinction in tissue distribution between SPE-15/HUM-3 and HUM-8. While SPE-15/HUM-3 exhibited specific expression in the gonads and neuronal tissue in the head, HUM-8 was exclusively localized in the intestinal epithelium. Overall, these findings align with the established tissue distributions and localizations of human MYO6.

Keywords: C. elegans; HUM-8; MYO6; SPE-15/HUM-3; actin.

Grants and funding

The author(s) declare financial support was received for the research, authorship, and/or publication of this article. This work was supported by a Trinity College Krishnan-Ang Studentship to RB, an MRC-funded PhD studentship to AJH (MC00076), and a Henry Wellcome Fellowship to CAJ. Work in the DM lab is supported by funding from the Biotechnology and Biological Sciences Research Council (BB/S005544/1 & BB/X007448/1) and in the FB lab through a program grant from the Medical Research Council (MR/S007776/1). CIMR is supported by the Wellcome Trust with an equipment grant (108415).