Case Studies in Cell Biology by Casem Merri Lynn;

Author:Casem, Merri Lynn; [Casem, Merri Lynn]
Language: eng
Format: epub
Publisher: Elsevier Science & Technology
Published: 2016-09-15T00:00:00+00:00

Keywords

rough endoplasmic reticulum

Golgi complex

COPI

COPII

VSV-G protein

small transport vesicle

cisternal maturation

procollagen

fusion protein

cell-free assay

Subchapter 8.1

Coat Proteins and Vesicle Transport [1]

Introduction

The pathway of exocytosis starts with the synthesis of a protein on the rough endoplasmic reticulum (RER). From there, the protein must travel through each of the compartments of the Golgi complex, finally arriving at the trans Golgi network (TGN) before being transported to the plasma membrane, lysosome, or vacuole. The collections of membrane-bound organelles that participate in exocytosis are part of the endomembrane system. It is generally accepted that proteins move along the exocytic pathway inside small transport vesicles. Transport vesicles are formed through a process of “budding” from the membrane of the RER or Golgi, capturing protein cargo in the process. Fusion of the vesicles with the membrane of the target organelle releases the protein cargo into that compartment. These vesicles carry a collection of peripheral proteins on the cytoplasmic side of their membranes, forming a “coat.” COPI and COPII are the two distinct types of coated vesicles associated with transport between the RER and the Golgi complex.

Three models were developed to explain the role of coated vesicles in exocytosis. The first model proposed that COPII vesicles were responsible for the anterograde (forward) movement of materials in the cell. The second model proposed that both COPI and COPII vesicles moved material in parallel, independent of anterograde pathways. The third model proposed a sequential role for coated vesicles. In this model the COPII vesicles carry material from the RER to an intermediate compartment. COPI vesicles are then formed from the intermediate compartment to carry the material to the cis Golgi. The work presented in this case study seeks to determine which of these models is correct.

▪ Research/review the types of proteins that are synthesized on the RER.

▪ Summarize how a newly synthesized protein is modified from the time it enters the lumen of the RER to the time it reaches the trans Golgi network.

▪ Describe another example of a coated vesicle found in cells.

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