title: Basolateral sorting of the Mg²⁺ transporter CNNM4 requires interaction with AP-1A and AP-1B.
abstract: Ancient conserved domain protein/cyclin M (CNNM) 4 is an evolutionarily conserved Mg(2+) transporter that localizes at the basolateral membrane of the intestinal epithelia. Here, we show the complementary importance of clathrin adaptor protein (AP) complexes AP-1A and AP-1B in basolateral sorting of CNNM4. We first confirmed the basolateral localization of both endogenous and ectopically expressed CNNM4 in Madin-Darby Canine Kidney cells, which form highly polarized epithelia in culture. Single knockdown of μ1B, a cargo-recognition subunit of AP-1B, did not affect basolateral localization, but simultaneous knockdown of the μ1A subunit of AP-1A abrogated localization. Mutational analyses showed the importance of three conserved dileucine motifs in CNNM4 for both basolateral sorting and interaction with μ1A and μ1B. These results imply that CNNM4 is sorted to the basolateral membrane by the complementary function of AP-1A and AP-1B.
authors.affiliation: Department of Cellular Regulation, Research Institute for Microbial Diseases, Osaka University, 3-1 Yamadaoka, Suita, Osaka 565-0871, Japan; Laboratory of Health Chemistry, Graduate School of Pharmaceutical Sciences, Tohoku University, 6-3 Aoba, Aramaki, Aoba-ku, Sendai, Miyagi 980-8578, Japan.
authors.forename: Yusuke
authors.initials: Y
authors.lastname: Hirata
authors.affiliation: Department of Cellular Regulation, Research Institute for Microbial Diseases, Osaka University, 3-1 Yamadaoka, Suita, Osaka 565-0871, Japan.
authors.forename: Yosuke
authors.initials: Y
authors.lastname: Funato
authors.affiliation: Department of Cellular Regulation, Research Institute for Microbial Diseases, Osaka University, 3-1 Yamadaoka, Suita, Osaka 565-0871, Japan. Electronic address: hmiki@biken.osaka-u.ac.jp.
authors.forename: Hiroaki
authors.initials: H
authors.lastname: Miki
mesh_terms: D033961:Adaptor Protein Complex 1 / Q000737:chemistry / Q000502:physiology*; D033966:Adaptor Protein Complex beta Subunits / Q000737:chemistry / Q000502:physiology*; D033983:Adaptor Protein Complex mu Subunits / Q000737:chemistry / Q000502:physiology*; D020816:Amino Acid Motifs; D000595:Amino Acid Sequence; D000818:Animals; D019921:Biotinylation; D019556:COS Cells; D027682:Cation Transport Proteins / Q000378:metabolism*; D002460:Cell Line; D002462:Cell Membrane / Q000378:metabolism; D002522:Chlorocebus aethiops; D018076:DNA, Complementary / Q000378:metabolism; D004285:Dogs; D005786:Gene Expression Regulation; D006801:Humans; D008274:Magnesium / Q000737:chemistry*; D026901:Membrane Transport Proteins / Q000378:metabolism; D008856:Microscopy, Fluorescence; D008969:Molecular Sequence Data; D009154:Mutation; D021381:Protein Transport; D034622:RNA Interference
chemical_list: C439126:AP1B1 protein, human; D033961:Adaptor Protein Complex 1; D033966:Adaptor Protein Complex beta Subunits; D033983:Adaptor Protein Complex mu Subunits; C539261:CNNM4 protein, human; D027682:Cation Transport Proteins; D018076:DNA, Complementary; D026901:Membrane Transport Proteins; D008274:Magnesium
keywords: AP-1A; AP-1B; Basolateral sorting; CNNM4; Dileucine motif; Mg(2+) transport