17. When some viruses infect cells, they interfere with the cells’ normal secret

Question

17. When some viruses infect cells, they interfere with the cells’ normal secretory path. For
example, cells infected with poliovirus show a massive accumulation of vesicles, as well as an
apparent loss of the normal golgi apparatus structure (there are no identifiable golgi cisternae
present in the infected cells). Jack has spent years in a lab studying how poliovirus alters the
secretory path. His hypothesis is that these vesicles mostly come from the ER; he is at a loss to
explain why he can’t find the Golgi apparatus in the infected cells.

A. If Jack’s hypothesis is correct and the vesicles are derived from the ER, what process could
the polio infection interfere with to give this phenotype?

B. List the key protein families necessary for this process (in A) and briefly describe the role of
these proteins.

C. Help Jack formulate a hypothesis to explain the disappearance of the Golgi in the infected
cells.

Explanation / Answer

A. The polio infection interferes with the secretory pathway from ER to Golgi. ----------------------- B. The key proteins necessary for secretory pathway are the coat proteins. The coat protein for ER is COPII. The chaperone proteins present in the ER help the protein to fold correctly. ---------------------------- C. The vesicles which move from ER to Golgi are added to the cis face of Golgi. These vesicles merge with the Golgi. From the trans face of Golgi we see the budding of vesicles which transport proteins to other organelles of the cell. Hence, in Golgi, we see an addition of vesicles at the cis face and removal of vesicles at the trans face. The vesicles added at the cis face are slowly moved forward to replace the vesicles removed at the trans face. This maintains the Golgi apparatus. -------------------------- In polio infected cells, the secretory pathway from ER to Golgi is blocked. The vesicles which transport proteins from ER to Golgi are accumulated in the ER. This accumulation plays a role in the disappearance of Golgi apparatus from polio infected cells. In the Golgi, vesicles are formed and removed at the trans face as usual, but no vesicles are added to the cis face of the Golgi. The vesicles formed at the trans face slowly reduce the Golgi till it gradually disappears.

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