Palmitoylation-dependent plasma membrane transport but lipid raft-independent signaling by linker for activation of T cells.
Linker for activation of T cells (LAT) is a dually palmitoylated transmembrane adaptor protein essential for T cell development and activation. However, whether LAT palmitoylation and/or lipid raft localization are required for its function is controversial. To address this question, we used a combination of biochemical, imaging, and genetic approaches, including LAT retrovirus-transduced mouse T cells and bone marrow chimeric mice. A nonpalmitoylated, non-lipid raft-residing mutant of transmembrane LAT could not reconstitute T cell development in bone marrow chimeric mice. This mutant was absent from the plasma membrane (PM) and was restricted mainly to the Golgi apparatus. A chimeric, nonpalmitoylated LAT protein consisting of the PM-targeting N-terminal sequence of Src kinase and the LAT cytoplasmic domain (Src-LAT) localized as a peripheral membrane protein in the PM, but outside lipid rafts. Nevertheless, Src-LAT restored T cell development and activation. Lastly, monopalmitoylation of LAT on Cys(26) (but not Cys(29)) was required and sufficient for its PM transport and function. Thus, the function of LAT in T cells requires its PM, but not raft, localization, even when expressed as a peripheral membrane protein. Furthermore, LAT palmitoylation functions primarily as a sorting signal required for its PM transport.
Hundt
Matthias
M
Division of Cell Biology, La Jolla Institute for Allergy & Immunology, La Jolla, CA 92037, USA.
Harada
Yohsuke
Y
De Giorgio
Lauren
L
Tanimura
Natsuko
N
Zhang
Weiguo
W
Altman
Amnon
A
D048868:Adaptor Proteins, Signal Transducing / Q000378:metabolism*; D000818:Animals; D002462:Cell Membrane / Q000378:metabolism*; D002678:Chimera; D054878:Lipoylation; D021962:Membrane Microdomains; D008565:Membrane Proteins / Q000378:metabolism*; D051379:Mice; D010750:Phosphoproteins / Q000378:metabolism*; D021381:Protein Transport; D015398:Signal Transduction; D013601:T-Lymphocytes; D019061:src-Family Kinases
D048868:Adaptor Proteins, Signal Transducing; C491734:Lat protein, mouse; D008565:Membrane Proteins; D010750:Phosphoproteins; D019061:src-Family Kinases