Question

Please answer the following questions based on this paper.

Paper: Kaiser CA & Schekman R (1990) Distinct sets of SEC genes govern transport vesicle formation and fusion early in the secretory pathway.

Briefly describe what was known about trafficking from the ER to the Golgi prior to this study. What was the main motivation for the study?

What were the alternative models that were discussed for the mechanism of transport between the ER and the Golgi?

What was the hypothesis and prediction of the paper?

Briefly (1 paragraph or less) explain the experimental strategy and results from this paper.

Why do you think the authors chose to use temperature-sensitive mutants? What are the advantages/disadvantages to this experimental strategy?

Randy Schekman, James Rothman, and Thomas Südhof shared the Nobel Prize in Physiology or Medicine in 2013. This paper is listed as one of the key publications. Why do you think this paper was so important in the field?

If you were a researcher in this lab, what experiment would you do next?

Answer 1

A. Previous reports had already demonstrated that secreted proteins cross various membrane-bounded compartments in their transport route to the cell surface. The literature clearly indicated that vesicle carriers budding from the donor compartment assisted in protein transport by fusing with the acceptor compartment. An intermediate stage of a vesicle was suggested to be formed between the ER and the Golgi apparatus.

This study was directed towards detecting the role of vesicle budding and vesicle fusion proteins for the vesicle-mediated transport between ER and Golgi apparatus.

B. Other alternatives for the transport from ER to Golgi apparatus included transient tubular connection formation between the ER and Golgi apparatus or, direct transformation of the ER region into the cis Golgi compartment for transport.

C. The hypothesis of the paper was- to study the interaction of certain gene proteins for vesicle budding and vesicle fusion process.

D. Experimental sections of the study included-

• Electron microscopy was used to visualize the changes in membrane structure morphology after inducing mutation in genes necessary for the transport of secretory protein from the ER.
• Analysis of the epistatic relationship between 2 mutant groups.
• Analyzing the post-translational modification of proteins by incubating cells with or without cycloheximide.
• Studying the genetic interaction between mutation groups.