Singh, Jagjot

DNAJC5, an HSP40 member, supports synaptic vesicle release and protein folding byactivating HSP70 ATPase activity. In humans, it localizes to presynaptic terminals and endomembrane compartments that are involved in protein trafficking. Mutations in DNAJC5 cause CLN4 disease, a rare adult-onset Batten disease. Dictyostelium discoideum, a model for neurodegenerative research, encodes a putative homolog of DNAJC5, Dnajc5 (DDB0306688), which remains uncharacterized. This study examined Dnajc5 localization and function in D. discodieum. Dnajc5 localized to the endoplasmic reticulum, cytoplasm and nucleolus under both growth and starvation conditions, suggesting a role in proteostasis. Unlike human DNAJC5, Dnajc5 was absent from endomembrane compartments and extracellularly during starvation. Protein quantification revealed increased levels during early development, peaking at the mound stage, and declining thereafter—paralleling gene expression. Immunoprecipitation of Dnajc5 showed no serine phosphorylation or ubiquitination, unlike human DNAJC5. These findings suggest functional differences despite a possible common role in proteostasis.

Author Keywords: actinomycin- D, CLN4, Dictyostelium discoiduem, DNAJC5, Immunoprecipitation, multicellular development