Cell Biology

Caught in Traffic

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Science  29 Jun 2007:
Vol. 316, Issue 5833, pp. 1815
DOI: 10.1126/science.316.5833.1815a

A number of inherited human disorders are thought to be caused by functional alterations in the primary cilium, a hairlike extension of the cell membrane whose critical role in cellular signaling has been receiving increasing attention. Bardet-Biedl syndrome (BBS) is one such disorder that has been linked to cilia through studies of animal models. BBS affects many different organ systems and its characteristic features include obesity, retinal degeneration, and kidney abnormalities. Because mutations in at least a dozen distinct genes can cause BBS, and many of these genes are functionally undefined, the description of a simple molecular model for disease pathogenesis has been an elusive goal. Important progress toward that goal is reported by Nachury et al., who show that 7 of the 12 known BBS gene products form a stable 450-kD protein complex, dubbed the “BBSome,” that localizes to the ciliary membrane and physically associates with Rabin8, a nucleotide exchange factor specific for the Rab8 small guanosine triphosphatase. The authors propose that the BBSome promotes trafficking of specific transmembrane proteins (such as rhodopsin in the case of retinal photoreceptor cells) from the cell to the primary cilium, where they perform critical signaling functions. Conceivably, each organ-specific symptom of BBS could arise through the mistargeting of specific cilium-localized signaling receptors critical to that organ. — PAK

Cell 129, 1201 (2007).

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