title: Mu1B, a novel adaptor medium chain expressed in polarized epithelial cells.
abstract: The apical and basolateral plasma membrane domains of polarized epithelial cells contain distinct sets of integral membrane proteins. Biosynthetic targeting of proteins to the basolateral plasma membrane is mediated by cytosolic tail determinants, many of which resemble signals involved in the rapid endocytosis or lysosomal targeting. Since these signals are recognized by adaptor proteins, we hypothesized that there could be epithelial-specific adaptors involved in polarized sorting. Here, we report the identification of a novel member of the adaptor medium chain family, named mu1B, which is closely related to the previously described mu1A (79% amino acid sequence identity). Northern blotting and in situ hybridization analyses reveal the specific expression of mu1B mRNA in a subset of polarized epithelial and exocrine cells. Yeast two-hybrid analyses show that mu1B is capable of interacting with generic tyrosine-based sorting signals. These observations suggest that mu1B may be involved in protein sorting events specific to polarized cells.
authors.affiliation: Department of Molecular Genetics, Chiba University Graduate School of Medicine, Japan. ohno@gene.m.chiba-u.ac.jp
authors.forename: H
authors.initials: H
authors.lastname: Ohno
authors.forename: T
authors.initials: T
authors.lastname: Tomemori
authors.forename: F
authors.initials: F
authors.lastname: Nakatsu
authors.forename: Y
authors.initials: Y
authors.lastname: Okazaki
authors.forename: R C
authors.initials: RC
authors.lastname: Aguilar
authors.forename: H
authors.initials: H
authors.lastname: Foelsch
authors.forename: I
authors.initials: I
authors.lastname: Mellman
authors.forename: T
authors.initials: T
authors.lastname: Saito
authors.forename: T
authors.initials: T
authors.lastname: Shirasawa
authors.forename: J S
authors.initials: JS
authors.lastname: Bonifacino
mesh_terms: D033961:Adaptor Protein Complex 1; D033965:Adaptor Protein Complex alpha Subunits; D033983:Adaptor Protein Complex mu Subunits; D033942:Adaptor Proteins, Vesicular Transport; D000595:Amino Acid Sequence; D000818:Animals; D001483:Base Sequence; D002460:Cell Line; D016764:Cell Polarity; D002522:Chlorocebus aethiops; D003001:Cloning, Molecular; D018076:DNA, Complementary; D004847:Epithelial Cells / Q000378:metabolism*; D019073:HT29 Cells; D006367:HeLa Cells; D006801:Humans; D008565:Membrane Proteins / Q000096:biosynthesis* / Q000235:genetics; D051379:Mice; D008810:Mice, Inbred C57BL; D008969:Molecular Sequence Data; D051381:Rats; D017386:Sequence Homology, Amino Acid; D013552:Swine; D014018:Tissue Distribution; D014407:Tumor Cells, Cultured
chemical_list: C438883:AP1M1 protein, human; C499064:AP1M2 protein, human; D033961:Adaptor Protein Complex 1; D033965:Adaptor Protein Complex alpha Subunits; D033983:Adaptor Protein Complex mu Subunits; D033942:Adaptor Proteins, Vesicular Transport; C499063:Ap1m1 protein, mouse; C438884:Ap1m2 protein, mouse; D018076:DNA, Complementary; D008565:Membrane Proteins; C499066:adaptor protein complex 1, mu 1 subunit; C499065:adaptor protein complex 1, mu 2 subunit