In today’s new issue of JCB, Gong et al. describe how a protein called Fsp27 promotes the growth of lipid droplets in fat-storing adipocytes. Fsp27 localizes to the site where neighboring droplets contact each other, and facilitates the transfer of lipids from the smaller to the larger droplet. More in this summary. Meanwhile, de Saint-Jean et al. describe how a protein called Osh4p exchanges sterols and phosphatidylinositol-4-phosphate between organelles in order to set up a sterol gradient across the different organelles of the secretory pathway. Tim Levine provides a comment on this surprising finding.
Bruns et al. identify a novel membrane-bound compartment in yeast called CUPS. This “Compartment for Unconventional Protein Secretion” contains many of the proteins required to deliver the Acyl-CoA-binding protein Acb1 to the surface of starving budding yeast via a recently-discovered pathway that sidesteps the usual secretory route through the ER and Golgi apparatus. You can learn more about the proteins that localize to CUPS, and how the organelle compares to similar compartments in the autophagy pathway, in this summary article.
And Garcia et al. reveal that the shape of septin filaments can be modulated by the incorporation of different septin subunits and by septin phosphorylation. Septins are a conserved family of GTPases that hetero-oligomerize into filamentous structures in order to control a variety of cellular processes, including budding yeast cytokinesis, where septins form an organized collar around the bud neck. Complexes containing the septin Cdc11 assemble into long, straight rods, but Garcia et al. find that substituting another septin, Shs1, in place of Cdc11 drives the formation of ring-shaped structures. Moreover, the phosphorylation of Shs1 can promote the assembly of septins into a gauze-like meshwork. Read more about how this all relates to septins’ functions at the yeast bud neck in this week’s In Focus.
Yamaguchi et al. perform some beautiful in vivo imaging to investigate how apoptosis contributes to neural tube closure in mouse embryonic brains (summary here) and Janes et al. examine the crosstalk between different subclasses of the Eph receptor tyrosine kinase family. This latter paper is covered in more detail in this month’s biobytes podcast, in which you can also hear Vania Braga describe her lab’s recent paper explaining how the cell junction protein Ajuba regulates the Rac GTPase at intercellular contacts. You can listen below or subscribe in iTunes.
That’s all for today, but don’t forget to check out all the other great papers published in today’s new issue. You can find them all on our table of contents.
Cover image courtesy of Zhiqi Sun.