Characterization of HAF-4- and HAF-9-localizing organelles as distinct organelles in Caenorhabditis elegans intestinal cells

Abstract

BackgroundThe intestinal cells of Caenorhabditis elegans are filled with heterogeneous granular organelles that are associated with specific organ functions. The best studied of these organelles are lipid droplets and acidified gut granules associated with GLO-1, a homolog of the small GTPase Rab38. In this study, we characterized a subset of the intestinal granules in which HAF-4 and HAF-9 localize on the membrane. HAF-4 and HAF-9 are ATP-binding cassette (ABC) transporter proteins that are homologous to the mammalian lysosomal peptide transporter TAPL (transporter associated with antigen processing-like, ABCB9).ResultsUsing transgenic worms expressing fluorescent protein-tagged marker proteins, we demonstrated that the HAF-4- and HAF-9-localizing organelles are not lipid droplets and do not participate in yolk protein transport. They were also ruled out as GLO-1-positive acidified gut granules. Furthermore, we clarified that the late endosomal protein RAB-7 localizes to the HAF-4- and HAF-9-localizing organelles and is required for their biogenesis.ConclusionsOur results indicate that the HAF-4- and HAF-9-localizing organelles are distinct intestinal organelles associated with the endocytic pathway.Electronic supplementary materialThe online version of this article (doi:10.1186/s12860-015-0076-2) contains supplementary material, which is available to authorized users.

Modular metabolite assembly inC. elegansdepends on carboxylesterases and formation of lysosome-related organelles

“…Consistent with the notion that lysosomes and LROs are degradation hotspots, many of the building blocks of the identified modular ascarosides and glucosides are derived from catabolic pathways, for example, anthranilic acid is derived from tryptophan catabolism, uric acid stems from purine metabolism, and the short chain ascarosides are the end products of peroxisomal β -oxidation of very long-chain precursors. Importantly, although our results indicate that carboxylesterases participate in glo-1 -dependent modular metabolite assembly, additional studies are required to clarify whether the intestinal compartments that carboxylesterases localize to also contain GLO-1 and the lysosomal marker LMP-1, as is the case for the autofluorescent LROs 22 .…”

“…1a) 14 . In addition to the autofluorescent LROs, several other types of intestinal granules have been characterized in C. elegans , including lipid droplets 21 and lysosome-related organelles that are not glo-1 -dependent 22 .…”

Modular metabolite assembly in Caenorhabditis elegans depends on carboxylesterases and formation of lysosome-related organelles

“…Additionally, it has been suggested that LROs may be involved in the production and secretion of diverse signaling molecules ( Dell'Angelica et al, 2000 ; Luzio et al, 2014 ), and the observation that glo-1 mutant worms are deficient in 4′-modified ascarosides suggested that intestinal organelles may serve as hubs for their assembly ( Figure 1a ; Panda et al, 2017 ). In addition to the autofluorescent LROs, several other types of intestinal granules have been characterized in C. elegans , including lipid droplets ( Cao et al, 2019 ) and lysosome-related organelles that are not glo-1 -dependent ( Tanji et al, 2016 ).…”

Biosynthesis of Modular Ascarosides in C. elegans

“…Importantly, the abundances of indole-3-carboxylic acid and N -succinyl octopamine in glo-1 mutants were similar or only slightly reduced relative to the wildtype, suggesting that abolishment of 4′-modified ascarosides in this mutant is not due to depletion of any of the building blocks (Figure S1 in the Supporting Information). In contrast, the amounts of 4′-modified ascarosides in cup-5(ar465) , haf-4(ok1042) , and haf-9(gk23) mutants, which are defective in the formation of non-acidic gut granules but do have acidic LROs, [15] are similar or increased relative to the wildtype (Figure S6). These results indicate that acidic LROs are required for the biosynthesis of all 4′-modified ascarosides, including icas#9 and osas#9, the biosynthesis of which specifically requires ACS-7 (Figure 4).…”