Sorting signals that mediate traffic of chitin synthase III between the TGN/endosomes and to the plasma membrane in yeast.
Traffic of the integral yeast membrane protein chitin synthase III (Chs3p) from the trans-Golgi network (TGN) to the cell surface and to and from the early endosomes (EE) requires active protein sorting decoded by a number of protein coats. Here we define overlapping signals on Chs3p responsible for sorting in both exocytic and intracellular pathways by the coats exomer and AP-1, respectively. Residues 19DEESLL24, near the N-terminal cytoplasmically-exposed domain, comprise both an exocytic di-acidic signal and an intracellular di-leucine signal. Additionally we show that the AP-3 complex is required for the intracellular retention of Chs3p. Finally, residues R374 and W391, comprise another signal responsible for an exomer-independent alternative pathway that conveys Chs3p to the cell surface. These results establish a role for active protein sorting at the trans-Golgi en route to the plasma membrane (PM) and suggest a possible mechanism to regulate protein trafficking.
Howard Hughes Medical Institute, Department of Molecular and Cell Biology, University of California, Berkeley, California, USA.
Trevor L
TL
Starr
Silvere
S
Pagant
Chao-Wen
CW
Wang
Randy
R
Schekman
D002462:Cell Membrane / Q000378:metabolism*; D002687:Chitin Synthase / Q000235:genetics / Q000302:isolation & purification / Q000378:metabolism*; D002846:Chromatography, Affinity; D011992:Endosomes / Q000378:metabolism*; D005089:Exocytosis; D006056:Golgi Apparatus / Q000378:metabolism*; D009154:Mutation; D021382:Protein Sorting Signals; D015003:Yeasts / Q000201:enzymology / Q000378:metabolism*
D021382:Protein Sorting Signals; D002687:Chitin Synthase