A multimeric membrane protein reveals 14-3-3 isoform specificity in forward transport in yeast.
Arginine (Arg)-based endoplasmic reticulum (ER) localization signals are sorting motifs involved in the quality control of multimeric membrane proteins. They are distinct from other ER localization signals like the C-terminal di-lysine [-K(X)KXX] signal. The Pmp2p isoproteolipid, a type I yeast membrane protein, reports faithfully on the activity of sorting signals when fused to a tail containing either an Arg-based motif or a -KKXX signal. This reporter reveals that the Arg-based ER localization signals from mammalian Kir6.2 and GB1 proteins are functional in yeast. Thus, the machinery involved in recognition of Arg-based signals is evolutionarily conserved. Multimeric presentation of the Arg-based signal from Kir6.2 on Pmp2p results in forward transport, which requires 14-3-3 proteins encoded in yeast by BMH1 and BMH2 in two isoforms. Comparison of a strain without any 14-3-3 proteins (Deltabmh2) and the individual Deltabmh1 or Deltabmh2 shows that the role of 14-3-3 in the trafficking of this multimeric Pmp2p reporter is isoform-specific. Efficient forward transport requires the presence of Bmh1p. The specific role of Bmh1p is not due to differences in abundance or affinity between the isoforms. Our results imply that 14-3-3 proteins mediate forward transport by a mechanism distinct from simple masking of the Arg-based signal.
Michelsen
Kai
K
Zentrum für Molekulare Biologie der Universität Heidelberg (ZMBH), Im Neuenheimer Feld 282, D-69120 Heidelberg, Germany.
Mrowiec
Thomas
T
Duderstadt
Karl E
KE
Frey
Steffen
S
Minor
Daniel L
DL
Mayer
Matthias P
MP
Schwappach
Blanche
B
D048948:14-3-3 Proteins / Q000378:metabolism*; D048868:Adaptor Proteins, Signal Transducing; D000595:Amino Acid Sequence; D001120:Arginine / Q000235:genetics / Q000378:metabolism; D004721:Endoplasmic Reticulum / Q000378:metabolism; D017353:Gene Deletion; D018628:Gene Dosage; D017930:Genes, Reporter / Q000235:genetics; D008565:Membrane Proteins / Q000737:chemistry / Q000235:genetics / Q000378:metabolism*; D008969:Molecular Sequence Data; D009419:Nerve Tissue Proteins / Q000737:chemistry / Q000235:genetics / Q000378:metabolism*; D010641:Phenotype; D024661:Potassium Channels, Inwardly Rectifying / Q000378:metabolism; D011485:Protein Binding; D020033:Protein Isoforms / Q000378:metabolism; D021122:Protein Subunits / Q000235:genetics / Q000378:metabolism; D021381:Protein Transport; D011510:Proteolipids / Q000737:chemistry / Q000235:genetics / Q000378:metabolism*; D018079:Receptors, GABA / Q000235:genetics / Q000378:metabolism; D012441:Saccharomyces cerevisiae / Q000737:chemistry / Q000378:metabolism*; D029701:Saccharomyces cerevisiae Proteins / Q000737:chemistry / Q000235:genetics / Q000378:metabolism*; D015398:Signal Transduction; D000099161:Kcnj11 Channel
D048948:14-3-3 Proteins; D048868:Adaptor Proteins, Signal Transducing; D001120:Arginine; D008565:Membrane Proteins; D009419:Nerve Tissue Proteins; D024661:Potassium Channels, Inwardly Rectifying; D020033:Protein Isoforms; D021122:Protein Subunits; D011510:Proteolipids; D018079:Receptors, GABA; D029701:Saccharomyces cerevisiae Proteins; D000099161:Kcnj11 Channel; C075852:BMH1 protein, S cerevisiae; C097164:BMH2 protein, S cerevisiae; C489078:PMP2 protein, S cerevisiae