Countercurrent distribution of two distinct SNARE complexes mediating transport within the Golgi stack.
Genetic and biochemical evidence has established that a SNARE complex consisting of syntaxin 5 (Sed5)-mYkt6 (Ykt6)-GOS28 (Gos1)-GS15 (Sft1) is required for transport of proteins across the Golgi stack in animals (yeast). We have utilized quantitative immunogold labeling to establish the cis-trans distribution of the v-SNARE GS15 and the t-SNARE subunits GOS28 and syntaxin 5. Whereas the distribution of the t-SNARE is nearly even across the Golgi stack from the cis to the trans side, the v-SNARE GS15 is present in a gradient of increasing concentration toward the trans face of the stack. This contrasts with a second distinct SNARE complex, also required for intra-Golgi transport, consisting of syntaxin 5 (Sed5)-membrin (Bos1)-ERS24 (Sec22)-rBet1 (Bet1), whose v-(rBet1) and t-SNARE subunits (membrin and ERS24), progressively decrease in concentration toward the trans face. Transport within the stack therefore appears to utilize countercurrent gradients of two Golgi SNAREpins and may involve a mechanism akin to homotypic fusion.
Volchuk
Allen
A
Department of Morphology, University of Geneva Medical School, Geneva, Switzerland.
Ravazzola
Mariella
M
Perrelet
Alain
A
Eng
William S
WS
Di Liberto
Maurizio
M
Varlamov
Oleg
O
Fukasawa
Masayoshi
M
Engel
Thomas
T
Söllner
Thomas H
TH
Rothman
James E
JE
Orci
Lelio
L
D000818:Animals; D001692:Biological Transport; D002352:Carrier Proteins / Q000378:metabolism; D002460:Cell Line; D002462:Cell Membrane / Q000378:metabolism; D002474:Cell-Free System; D004305:Dose-Response Relationship, Drug; D006056:Golgi Apparatus / Q000378:metabolism*; D006367:HeLa Cells; D006801:Humans; D007150:Immunohistochemistry; D007668:Kidney / Q000378:metabolism; D008565:Membrane Proteins / Q000378:metabolism; D008854:Microscopy, Electron; D008856:Microscopy, Fluorescence; D008954:Models, Biological; D011233:Precipitin Tests; D050765:Qa-SNARE Proteins; D050766:Qb-SNARE Proteins; D050767:Qc-SNARE Proteins; D050683:R-SNARE Proteins; D051381:Rats; D050600:SNARE Proteins; D033921:Vesicular Transport Proteins / Q000737:chemistry* / Q000378:metabolism
C098783:BET1 protein, rat; C107588:BET1L protein, human; C495951:Bet1l protein, rat; D002352:Carrier Proteins; C490972:GOSR1 protein, human; C491344:GOSR2 protein, human; C490971:Gosr1 protein, mouse; C099509:Gosr1 protein, rat; C491343:Gosr2 protein, rat; D008565:Membrane Proteins; D050765:Qa-SNARE Proteins; D050766:Qb-SNARE Proteins; D050767:Qc-SNARE Proteins; D050683:R-SNARE Proteins; C484373:SEC22A protein, human; D050600:SNARE Proteins; C098784:Sec22a protein, rat; D033921:Vesicular Transport Proteins; C491482:YKT6 protein, human; C491481:Ykt6 protein, rat