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Multiple cytosolic and transmembrane determinants are required for the trafficking of SCAMP1 via an ER–Golgi–TGN–PM pathway
Author(s) -
Cai Yi,
Jia Tianran,
Lam Sheung Kwan,
Ding Yu,
Gao Caiji,
San Melody Wan Yan,
Pimpl Peter,
Jiang Liwen
Publication year - 2011
Publication title -
the plant journal
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 3.058
H-Index - 269
eISSN - 1365-313X
pISSN - 0960-7412
DOI - 10.1111/j.1365-313x.2010.04469.x
Subject(s) - golgi apparatus , endoplasmic reticulum , microbiology and biotechnology , secretory pathway , transmembrane protein , transmembrane domain , cytosol , integral membrane protein , green fluorescent protein , transport protein , membrane protein , protein targeting , mutant , chemistry , biology , biochemistry , membrane , gene , receptor , enzyme
Summary How polytopic plasma membrane (PM) proteins reach their destination in plant cells remains elusive. Using transgenic tobacco BY‐2 cells, we previously showed that the rice secretory carrier membrane protein 1 (SCAMP1), an integral membrane protein with four transmembrane domains (TMDs), is localized to the PM and trans ‐Golgi network (TGN). Here, we study the transport pathway and sorting signals of SCAMP1 by following its transient expression in tobacco BY‐2 protoplasts and show that SCAMP1 reaches the PM via an endoplasmic reticulum (ER)–Golgi–TGN–PM pathway. Loss‐of‐function and gain‐of‐function analysis of various green fluorescent protein (GFP) fusions with SCAMP1 mutations further demonstrates that: (i) the cytosolic N‐terminus of SCAMP1 contains an ER export signal; (ii) the transmembrane domain 2 (TMD2) and TMD3 of SCAMP1 are essential for Golgi export; (iii) SCAMP1 TMD1 is essential for TGN‐to‐PM targeting; (iv) the predicted topology of SCAMP1 and its various mutants remain identical as demonstrated by protease protection assay. Therefore, both the cytosolic N‐terminus and TMD sequences of SCAMP1 play integral roles in mediating its transport to the PM via an ER–Golgi–TGN pathway.