title: The human ClC-4 protein, a member of the CLC chloride channel/transporter family, is localized to the endoplasmic reticulum by its N-terminus.
abstract: Despite considerable similarity in their amino acid sequences and structural features, the mammalian members of the CLC chloride channel/transporter family have different subcellular locations. The subcellular location and function of one of these members, hClC-4, is controversial. To characterize its cellular function, we investigated its tissue distribution and subcellular location. Expression was high in excitable tissues such as the nervous system and skeletal muscle. When heterologously expressed in HEK293 cells and in skeletal muscle fibers, hClC-4 localizes to the endoplasmic/sarcoplasmic reticulum (ER/SR) membranes, in contrast to hClC-3, which localizes to vesicular structures. This location was confirmed by identification of endogenous ClC-4 in membrane fractions from mouse brain homogenate enriched for the sarco-endoplasmic reticulum ATPase SERCA2, an ER/SR marker. To identify the motif responsible for ER localization of hClC-4, we generated hClC-4 truncations and chimeras between hClC-4 and hClC-3 or the unrelated plasma membrane protein Ly49E. A stretch of amino acids, residues 14-63, at the N-terminus constitutes a novel motif both necessary and sufficient for targeting hClC-4 and other membrane proteins to the ER.
authors.affiliation: MRC Clinical Sciences Centre, Imperial College Faculty of Medicine, Hammersmith Hospital Campus, Du Cane Rd., London W12 0NN, UK.
authors.forename: Hanneke
authors.initials: H
authors.lastname: Okkenhaug
authors.forename: Karsten-Henrich
authors.initials: KH
authors.lastname: Weylandt
authors.forename: David
authors.initials: D
authors.lastname: Carmena
authors.forename: Dominic J
authors.initials: DJ
authors.lastname: Wells
authors.forename: Christopher F
authors.initials: CF
authors.lastname: Higgins
authors.forename: Alessandro
authors.initials: A
authors.lastname: Sardini
mesh_terms: D000818:Animals; D002460:Cell Line; D018118:Chloride Channels / Q000737:chemistry / Q000235:genetics / Q000502:physiology*; D004721:Endoplasmic Reticulum / Q000502:physiology*; D006801:Humans; D007150:Immunohistochemistry; D007668:Kidney; D051379:Mice; D008810:Mice, Inbred C57BL; D018613:Microscopy, Confocal; D018485:Muscle Fibers, Skeletal / Q000502:physiology; D018482:Muscle, Skeletal / Q000502:physiology; D011994:Recombinant Proteins / Q000737:chemistry / Q000378:metabolism; D014162:Transfection
chemical_list: C484312:CLCN4 protein, human; D018118:Chloride Channels; D011994:Recombinant Proteins