Countercurrent Distribution of Two Distinct SNARE Complexes Mediating Transport within the Golgi Stack

• DOI: 10.1091/mbc.e03-08-0625
• Publication Date: 2004-01-26T20:33:19Z
• Authors: Allen Volchuk; Mariella Ravazzola; Alain Perrelet; William S. Eng; Maurizio Di Liberto; Oleg Varlamov; Masayoshi Fukasawa; Thomas Engel; Thomas H. Söllner; James E. Rothman; Lelio Orci
• Keywords: 0303 health sciences; Cell-Free System; Dose-Response Relationship, Drug; Qa-SNARE Proteins; Cell Membrane; Golgi Apparatus; Membrane Proteins; Biological Transport; Qb-SNARE Proteins; Kidney; Immunohistochemistry; Models, Biological; Precipitin Tests; Cell Line; Microscopy, Electron; 03 medical and health sciences; Microscopy, Fluorescence; Animals; Humans; Qc-SNARE Proteins; Carrier Proteins; HeLa Cells

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.