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The actomyosin ring bulks up

The Journal of Cell Biology
The Rockefeller University Press
Publication Date
DOI: 10.1083/jcb.1955iti2
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JCB_1955iti.indd In This Issue JCB • VOLUME 195 • NUMBER 5 • 2011704 Text by Mitch Leslie [email protected] VPS35 leaves endosomes lost in transition S luggish recycling of a protein-slicing enzyme could pro- mote Alzheimer’s disease (AD), Wen et al. show. A�, the protein that accumulates in the brains of AD patients, is formed when enzymes cut up its parental protein, known as amyloid precursor protein. One of those enzymes is �-secretase or BACE1. BACE1 cycles between the Golgi apparatus and the plasma membrane, traveling through endosomes on the way. A protein complex called the retromer helps transport proteins from endosomes to the Golgi. Previous studies have found reduced levels of two retromer components, including the protein VPS35, in the brains of AD patients. To fi nd out whether VPS35 affects AD, the team crossed two mouse lines to create animals that are prone to many AD symptoms and generate half the normal amount of VPS35. The mice displayed AD-like abnormalities earlier than their parental strains, and their brains accumulated more A�. Cells lacking VPS35 carried extra BACE1 in their endosomes. BACE1 is more active in the acidic interior of endosomes than in the more basic surroundings of the Golgi apparatus. Thus, by leaving more BACE1 trapped in endosomes, the decline in VPS35 levels could spur the formation of more A�. Although no VPS35 mutations have so far turned up in AD patients, the protein’s level in the brain dwindles with age in mice. The researchers suspect that certain AD risk factors, such as oxidative stress, also diminish VPS35 levels in the brain. Wen, L., et al. 2011. J. Cell Biol. jcb.201105109. The actomyosin ring bulks up C alvert et al. reveal that large fungal cells have more myosin II associated with their contractile rings than do smaller cells, which allows them to constrict the ring faster during cytokinesis. A recent study of C. elegans embryos showed t

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