New Issue: October 19th

There's a new edition of the JCB out today. We'll start our roundup with Tom Misteli's editorial on the recent JCB/New York Academy of Sciences meeting on the Cell Biology of Disease. Tom explains the rationale behind the meeting, much as he did in his introductory remarks to the conference. You can find our full coverage of the meeting by clicking here.

Elsewhere in this issue, our "In Focus" centers on the discovery by Canudas and Smith that cohesion between sister telomeres and centromeres is mediated by slightly different versions of the cohesin complex. Specifically, one of the cohesin subunits, Scc3, comes in two different flavors in vertebrate cells. Canudas and Smith show that Scc3^SA1 binds telomeres together, while Scc3^SA2 keeps sister centromeres close and, as you can read in my summary, telomere cohesion turns out to particularly important for the cell - defects in Scc3^SA2 or its binding partner TIN2 result in DNA double strand breaks and telomere loss. Meanwhile, Adelfalk et al. show that a meiosis-specific cohesin called Smc1beta is essential for maintaining telomere integrity and attaching them to the nuclear envelope.

Our cover image this issue is taken from Koto et al.'s investigation of caspase regulation during development of the Drosophila sensory organ. Caspases aren't just involved in apoptosis, they can also play constructive roles in development - promoting the elongation of sensory organ shaft cells, for example. Naturally, caspase activity needs to be tightly regulated to allow their function for only as long as it takes to promote development without causing cell death. Koto et al. reveal that temporal differences in the expression levels of a caspase inhibitor called DIAP1 help caspases walk this fine line.

Tsuruta et al. show how a lipid kinase called PIKfyve helps neurons avoid cell death. Neuronal death can arise from overexcitation of their voltage-gated calcium channels (during a stroke for example). As explained in this summary, Tsuruta et al. show that sustained activation leads to the recruitment of PIKfyve to calcium channels at the membrane, where it generates the phospholipid PtdIns(3,5)P₂. This, in turn, leads to the lysosomal targeting of the calcium channels, reducing calcium entry and cellular toxicity.

Next, we move from lysosome trafficking to melanosomal transport. Melanosomes are the specialized pigment granules of skin melanocytes that - similarly to lysosomes - arise from the endosomal system. Delevoye et al. show how two proteins, the clathrin adaptor AP-1 and the kinesin motor KIF13A, coordinate melanogenesis by positioning endosomes near to developing melanosomes and by sorting melanosome-specific cargo such as the enzymes that generate the melanin pigment. Moreover, Delevoye et al. provide some beautiful electron tomography to show that transport to the melanosomes is mediated by direct contact with tubules protruding from the endosomes - as in this image, where endosome tubules are in green and the melanosome is colored red. This paper will be the subject of our next biosights video, due in two weeks time but, in the meanwhile, you can read Lakkaraju et al.'s commentary on the article, which puts these findings into a nice perspective.

We also have a commentary (by Juliane Kellner and Pierre Coulombe) on a report by Vijayaraj et al. that keratins - the most neglected components of the cytoskeleton - have a surprising role in regulating protein synthesis. Mice lacking all their intermediate keratin filaments die in early embryogenesis due to severe growth retardation. It turns out that glucose transporters are mislocalized in the absence of keratins, leading to activation of the mTOR pathway and repression of protein synthesis. You can also learn more about this study in the latest edition of our biobytes podcast - also out today - in which Eun Choi speaks to the lead author Preethi Vijayaraj. And you can hear my interview with Greg Longmore on his lab's investigation of the antagonistic relationship between two rho GTPases in controlling cell shape that was published earlier this month. You can listen to biobytes by subscribing on iTunes, or by clicking here.

And don't forget to check out the rest of today's new articles by visiting our table of contents...