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The Syntaxins SYP31 and SYP81 Control ER–Golgi Trafficking in the Plant Secretory Pathway
Author(s) -
Bubeck Julia,
Scheuring David,
Hummel Eric,
Langhans Markus,
Viotti Corrado,
Foresti Ombretta,
Denecke Jürgen,
Banfield David K.,
Robinson David G.
Publication year - 2008
Publication title -
traffic
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 2.677
H-Index - 130
eISSN - 1600-0854
pISSN - 1398-9219
DOI - 10.1111/j.1600-0854.2008.00803.x
Subject(s) - golgi apparatus , endoplasmic reticulum , microbiology and biotechnology , syntaxin , secretory pathway , brefeldin a , secretion , biology , green fluorescent protein , fluorescence recovery after photobleaching , transport protein , secretory protein , exocytosis , biochemistry , gene , membrane
Overexpression of the Golgi and endoplasmic reticulum (ER) syntaxins SYP31 and SYP81 strongly inhibits constitutive secretion. By comparing the secreted reporter α‐amylase with the ER‐retained reporter α‐amylase‐HDEL, it was concluded that SYP81 overexpression inhibits both retrograde and anterograde transport, while SYP31 overexpression mainly affected anterograde transport. Of the other interacting SNAREs investigated, only the overexpression of MEMB11 led to an inhibition of protein secretion. Although the position of a fluorescent tag does not influence the correct localization of the fusion protein, only N‐terminal‐tagged SYP31 retained the ability of the untagged SNARE to inhibit transport. C‐terminal‐tagged SYP31 failed to exhibit this effect. Overexpression of both wild‐type and N‐terminal‐tagged syntaxins caused standard Golgi marker proteins to redistribute into the ER. Nevertheless, green fluorescent protein (GFP)–SYP31 was still visible as fluorescent punctae, which, unlike SYP31–GFP, were resistant to brefeldin A treatment. Immunogold electron microscopy showed that endogenous SYP81 is not only present at the ER but also in the cis Golgi, indicating that this syntaxin cycles between these two organelles. However, when expressed at non‐inhibitory levels, YFP–SYP81 was seen to locate principally to subdomains of the ER. These punctate structures were physically separated from the Golgi, suggesting that they might possibly reflect the position of ER import sites.