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

AUTOR(ES)

Volchuk, Allen

FONTE

The American Society for Cell Biology

RESUMO

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.

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