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NBD‐Labeled Phosphatidylcholine and Phosphatidylethanolamine are Internalized by Transbilayer Transport across the Yeast Plasma Membrane
Author(s) -
Grant Althea M.,
Hanson Pamela K.,
Malone Lynn,
Wylie Nichols J.
Publication year - 2001
Publication title -
traffic
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 2.677
H-Index - 130
eISSN - 1600-0854
pISSN - 1398-9219
DOI - 10.1034/j.1600-0854.2001.020106.x
Subject(s) - internalization , vacuole , endocytosis , phosphatidylethanolamine , microbiology and biotechnology , cytosol , biology , lipid bilayer fusion , vesicle , phosphatidylcholine , inner membrane , biochemistry , mitochondrion , biophysics , phospholipid , cytoplasm , membrane , receptor , enzyme
The internalization and distribution of fluorescent analogs of phosphatidylcholine (M‐C6‐NBD‐PC) and phosphatidylethanolamine (M‐C6‐NBD‐PE) were studied in Saccharomyces cerevisiae . At normal growth temperatures, M‐C6‐NBD‐PC was internalized predominantly to the vacuole and degraded. M‐C6‐NBD‐PE was internalized to the nuclear envelope/ER and mitochondria, was not transported to the vacuole, and was not degraded. At 2°C, both were internalized to the nuclear envelope/ER and mitochondria by an energy‐dependent, N ‐ethylmaleimide‐sensitive process, and transport of M‐C6‐NBD‐PC to and degradation in the vacuole was blocked. Internalization of neither phospholipid was reduced in the endocytosis‐defective mutant, end4‐1 . However, following pre‐incubation at 37°C, internalization of both phospholipids was inhibited at 2°C and 37°C in sec mutants defective in vesicular traffic. The sec18/NSF mutation was unique among the sec mutations in further blocking M‐C6‐NBD‐PC translocation to the vacuole suggesting a dependence on membrane fusion. Based on these and previous observations, we propose that M‐C6‐NBD‐PC and M‐C6‐NBD‐PE are transported across the plasma membrane to the cytosolic leaflet by a protein‐mediated, energy‐dependent mechanism. From the cytosolic leaflet, both phospholipids are spontaneously distributed to the nuclear envelope/ER and mitochondria. Subsequently, M‐C6‐NBD‐PC, but not M‐C6‐NBD‐PE, is sorted by vesicular transport to the vacuole where it is degraded by lumenal hydrolases.