How do Sec bodies form?

The Rabouille group of the Hubrecht Institute found how Sec bodies, a protection mechanism of cells under stress, are formed. The study is published on the website of eLife this week.

When cells are stressed (too hot, not enough food, noxious environment), they stop growing, and they store important molecular machines by putting them into large structures membrane-less where they are protected. These structures are called stress assemblies. Importantly, when the stress is relieved, these assemblies dissolve and the machines start working again.

One of these machines is made of components associated with the ‘exit sites’ of the endoplasmic reticulum (ER), where newly constructed proteins are produced.  Sec16 is a key protein of these ER exit sites. When cells from fruit flies are deprived of amino-acids, Sec16 and other components are stored into large stress assemblies, the Sec bodies. Sec bodies are important for cell survival during stress. When they cannot form, the cells do not cope with the starvation and die.

The main question of the study was to answer how Sec bodies are formed. Led by group leader Catherine Rabouille, Angelica Aguilera-Gomez et al. investigated how cells sense the shortage of amino-acids in their environment and how this is signaled to the exit sites components in such a way that they form Sec bodies.

The scientists found that amino-acid starvation activates an enzyme called PARP16 that modifies Sec16. This modification is enough to result in the formation of Sec bodies. Furthermore, they visualized this modification with a special design that they could follow in the microscope. Importantly, PARP16 is a key factor for the cell to survive the stress of amino-acid starvation. Furthermore, Sec16 is now considered as a protein central to the response to the stress of amino-acid starvation.

It is likely that more factors are modified by PARP16, and the scientists will investigate how exactly this modification leads to the formation of Sec bodies.

https://www-ncbi-nlm-nih-gov.proxy.library.uu.nl/pubmed/27874829

PMID: 27874829

DOI:10.7554/eLife.21475