Rme-1 regulates the recycling of the cystic fibrosis transmembrane conductance regulator.
Endocytic motifs in the carboxyl terminus of cystic fibrosis transmembrane conductance regulator (CFTR) direct internalization from the plasma membrane by clathrin-mediated endocytosis. However, the fate of such internalized CFTR has remained unknown. Internalized membrane proteins can be either targeted for degradation or recycled back to the plasma membrane. Using cell surface biotinylation and antibody uptake studies, we show that CFTR undergoes constitutive endocytosis and recycling back to the plasma membrane. Expression of dominant negative Rme-1 (a protein that regulates exit from the endosomal recycling compartment) in CFTR-expressing cells results in the expansion of recycling compartments. Transferrin, a marker for the endosomal recycling compartment, and CFTR accumulate in these enlarged recycling endosomes. Such accumulation leads to a loss of cell surface CFTR because it is prevented from being recycled back to the cell surface. In contrast, traffic of the low-density lipoprotein (LDL) is unaffected by the expression of dominant negative Rme-1. In addition, chimeras containing the extracellular domain of the transferrin receptor and the carboxyl terminal tail of CFTR also enter Rme-1-regulated recycling compartments and accumulate in these compartments containing dominant negative Rme-1, suggesting that in addition to endocytic signals, the carboxyl terminal tail of CFTR also contains intracellular traffic information.
Picciano
John A
JA
Cystic Fibrosis Research Center, Department of Cell Biology and Physiology, University of Pittsburgh School of Medicine, 3500 Terrace Street, Pittsburgh, PA 15261, USA.
Ameen
Nadia
N
Grant
Barth D
BD
Bradbury
Neil A
NA
D048868:Adaptor Proteins, Signal Transducing; D000818:Animals; D016466:CHO Cells; D002135:Calcium-Binding Proteins / Q000096:biosynthesis* / Q000235:genetics; D002460:Cell Line; D006224:Cricetinae; D019005:Cystic Fibrosis Transmembrane Conductance Regulator / Q000096:biosynthesis* / Q000235:genetics; D004705:Endocytosis / Q000502:physiology*; D005786:Gene Expression Regulation / Q000502:physiology; D006801:Humans; D047908:Intracellular Signaling Peptides and Proteins; D010750:Phosphoproteins / Q000096:biosynthesis* / Q000235:genetics; D021381:Protein Transport / Q000502:physiology
D048868:Adaptor Proteins, Signal Transducing; C505032:CFTR protein, human; D002135:Calcium-Binding Proteins; C486206:EPS15 protein, human; D047908:Intracellular Signaling Peptides and Proteins; D010750:Phosphoproteins; D019005:Cystic Fibrosis Transmembrane Conductance Regulator