In today’s new edition of JCB, Carroll-Portillo et al. reveal that mast cells form physical contacts with dendritic cells to facilitate the transfer of antigens inside exosomes. The dendritic cells can then present these antigens to T cells in order to stimulate an immune response. You can learn more about this new type of immune cell interaction in this week’s In Focus.
Hong et al. demonstrate that the phospholipid PI(3,5)P2 regulates the dynamics of branched actin networks on the surface of endosomes. As explained here, the phospholipid binds to the actin regulatory protein cortactin, removing it from branched actin filaments so that their stability is decreased. In the absence of PI(3,5)P2, therefore, cortactin accumulates on late endosomes and actin turnover is reduced.
DeGeer et al. describe how the chaperone protein Hsc70 shepherds a key guanine nucleotide exchange factor to the tips of growing axons. Hsc70 delivers the exchange factor Trio, which activates the small GTPase Rac in response to the axonal guidance cue netrin-1. Embryonic mice expressing a defective form of Hsc70 fail to undergo normal brain development. More here.
Xia et al. describe a way to force cancer cells to destroy a key metabolic enzyme they need to survive. As described here, the researchers find that simultaneously treating cancer cells – but not healthy cells – with inhibitors of both autophagy and the receptor tyrosine kinase FLT3 induces the degradation of hexokinase II, which catalyzes the first step of glycolysis.
Meanwhile, Schweizer et al. describe how a membranous spindle envelope helps numerous proteins accumulate around the mitotic spindle in order to facilitate bipolar spindle assembly and accurate chromosome segregation. Paul Maddox and Anne-Marie Ladouceur comment on the paper here, while senior author Helder Maiato discusses his group’s findings in this month’s biosights video podcast, which you can watch below or subscribe to in iTunes.
And finally, as always, don’t forget to check the JCB table of contents to see all the other papers published in today’s issue!
Cover image showing the accumulation of actin (red) and cortactin (green) on late endosomes (blue) in the absence of PI(3,5)P2 © 2015 Hong et al.