Control of Golgi morphology and function by Sed5 t-SNARE phosphorylation.
Previously, we demonstrated that the phosphorylation of t-SNAREs by protein kinase A (PKA) affects their ability to participate in SNARE complexes and to confer endocytosis and exocytosis in yeast. Here, we show that the presumed phosphorylation of a conserved membrane-proximal PKA consensus site (serine-317) in the Sed5 t-SNARE regulates endoplasmic reticulum (ER)-Golgi transport, as well as Golgi morphology. Sed5 is a phosphoprotein, and both alanine and aspartate substitutions in serine-317 directly affect intracellular protein trafficking. The aspartate substitution results in elaboration of the ER, defects in Golgi-ER retrograde transport, an accumulation of small transport vesicles, and the inhibition of growth of most cell types. In contrast, the alanine substitution has no deleterious effects upon transport and growth, but results in ordering of the Golgi into a structure reminiscent of mammalian apparatus. This structure seems to require the recycling of Sed5, because it was found not to occur in sec21-2 cells that are defective in retrograde transport. Thus, a cycle of Sed5 phosphorylation and dephosphorylation is required for normal t-SNARE function and may choreograph Golgi ordering and dispersal.
Weinberger
Adina
A
Department of Molecular Genetics, Weizmann Institute of Science, Rehovot 76100, Israel.
Kamena
Faustin
F
Kama
Rachel
R
Spang
Anne
A
Gerst
Jeffrey E
JE
D000595:Amino Acid Sequence; D019943:Amino Acid Substitution; D022181:COP-Coated Vesicles / Q000378:metabolism / Q000648:ultrastructure; D017868:Cyclic AMP-Dependent Protein Kinases / Q000378:metabolism*; D004721:Endoplasmic Reticulum / Q000378:metabolism / Q000648:ultrastructure; D006056:Golgi Apparatus / Q000378:metabolism* / Q000648:ultrastructure; D016253:Microscopy, Immunoelectron; D008969:Molecular Sequence Data; D010766:Phosphorylation; D021381:Protein Transport; D050765:Qa-SNARE Proteins / Q000378:metabolism*; D050600:SNARE Proteins / Q000378:metabolism*; D012441:Saccharomyces cerevisiae / Q000378:metabolism* / Q000648:ultrastructure; D029701:Saccharomyces cerevisiae Proteins / Q000378:metabolism*; D012694:Serine / Q000378:metabolism
D050765:Qa-SNARE Proteins; D050600:SNARE Proteins; D029701:Saccharomyces cerevisiae Proteins; C077554:Sed5 protein, S cerevisiae; D012694:Serine; D017868:Cyclic AMP-Dependent Protein Kinases