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.
Highlights
The intestinal cells of Caenorhabditis elegans are filled with heterogeneous granular organelles that are associated with specific organ functions
We reported that HAF-4 and HAF-9, ATPbinding cassette (ABC) transporter proteins that are homologous to the mammalian lysosomal peptide transporter Transporter associated with antigen processing-like (TAPL), localize to the membrane of a subset of intestinal granular organelles approximately 2 μm in diameter from the late larval to adult stages [17]
Further investigation using the late endosomal protein RAB-7 revealed that the HAF-4- and HAF-9localizing organelles are distinct intestinal organelles associated with the endocytic pathway
Summary
The 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 Rab. The intestine of Caenorhabditis elegans is a multifunctional organ involved in the uptake, metabolism, storage, and distribution of nutrients, as well as in detoxification and immune defense [1]. It consists of a tube comprising only 20 epithelial cells that are not replaced after embryonic development; each intestinal cell is considered to have multiple functions throughout the life of the animal. Some of the physiological roles of gut granules have been identified, such as the storage of zinc [10] and cholesterol [11], and signaling for aging [12], their overall functions remain poorly understood
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