Normal formation of a subset of intestinal granules in Caenorhabditis elegans requires ATP-binding cassette transporters HAF-4 and HAF-9, which are highly homologous to human lysosomal peptide transporter TAP-like.
TAP-like (TAPL; ABCB9) is a half-type ATP-binding cassette (ABC) transporter that localizes in lysosome and putatively conveys peptides from cytosol to lysosome. However, the physiological role of this transporter remains to be elucidated. Comparison of genome databases reveals that TAPL is conserved in various species from a simple model organism, Caenorhabditis elegans, to mammals. C. elegans possesses homologous TAPL genes: haf-4 and haf-9. In this study, we examined the tissue-specific expression of these two genes and analyzed the phenotypes of the loss-of-function mutants for haf-4 and haf-9 to elucidate the in vivo function of these genes. Both HAF-4 and HAF-9 tagged with green fluorescent protein (GFP) were mainly localized on the membrane of nonacidic but lysosome-associated membrane protein homologue (LMP-1)-positive intestinal granules from larval to adult stage. The mutants for haf-4 and haf-9 exhibited granular defects in late larval and young adult intestinal cells, associated with decreased brood size, prolonged defecation cycle, and slow growth. The intestinal granular phenotype was rescued by the overexpression of the GFP-tagged wild-type protein, but not by the ATP-unbound form of HAF-4. These results demonstrate that two ABC transporters, HAF-4 and HAF-9, are related to intestinal granular formation and some other physiological aspects.
Kawai
Hiromi
H
Department of Molecular Biology and Biochemistry, Graduate School of Pharmaceutical Sciences, Osaka University, Suita, Osaka 565-0871, Japan.
Tanji
Takahiro
T
Shiraishi
Hirohisa
H
Yamada
Mitsuo
M
Iijima
Ryoko
R
Inoue
Takao
T
Kezuka
Yasuko
Y
Ohashi
Kazuaki
K
Yoshida
Yasuo
Y
Tohyama
Koujiro
K
Gengyo-Ando
Keiko
K
Mitani
Shohei
S
Arai
Hiroyuki
H
Ohashi-Kobayashi
Ayako
A
Maeda
Masatomo
M
D018528:ATP-Binding Cassette Transporters / Q000737:chemistry / Q000378:metabolism*; D000595:Amino Acid Sequence; D000818:Animals; D017173:Caenorhabditis elegans / Q000166:cytology / Q000254:growth & development / Q000378:metabolism* / Q000648:ultrastructure; D029742:Caenorhabditis elegans Proteins / Q000378:metabolism*; D003594:Cytoplasmic Granules / Q000378:metabolism* / Q000648:ultrastructure; D017353:Gene Deletion; D049452:Green Fluorescent Proteins / Q000378:metabolism; D006801:Humans; D007413:Intestinal Mucosa / Q000378:metabolism*; D007422:Intestines / Q000166:cytology / Q000648:ultrastructure; D008247:Lysosomes / Q000378:metabolism; D008562:Membrane Glycoproteins / Q000378:metabolism; D008969:Molecular Sequence Data; D009928:Organ Specificity; D010641:Phenotype; D021381:Protein Transport; D011993:Recombinant Fusion Proteins / Q000378:metabolism; D017386:Sequence Homology, Amino Acid
D018528:ATP-Binding Cassette Transporters; D029742:Caenorhabditis elegans Proteins; C543630:HAF-4 protein, C elegans; C543631:HAF-9 protein, C elegans; C413182:LMP-1 protein, C elegans; D008562:Membrane Glycoproteins; D011993:Recombinant Fusion Proteins; C477327:transporter associated with antigen processing (TAP); D049452:Green Fluorescent Proteins