Cell Biology

Staying in Place

Science Signaling  27 Jul 2010:
Vol. 3, Issue 132, pp. ec233
DOI: 10.1126/scisignal.3132ec233

The primary cilium is found on nearly all mammalian cells and is a key regulatory organelle for proper signal transduction throughout development and in adults. Extracellular signal transduction, such as that promoted by Sonic hedgehog (Shh), requires the enrichment of receptors and downstream signaling components in the ciliary membrane. Intraflagellar transport is involved in selective trafficking of proteins into the cilium, but it is not known how these proteins are retained in the cilium. It has been speculated that a diffusion barrier exists at the base of the ciliary membrane. Now, Hu et al. demonstrate directly that a membrane diffusion barrier is indeed present at the base of the ciliary membrane. SEPT2, a member of the septin family that also forms a diffusion barrier in budding yeast and mammalian sperm membranes, localizes to the base of the ciliary membrane and is required for ciliogenesis, ciliary membrane protein localization, and cilium-dependent Shh signaling.

Q. Hu, L. Milenkovic, H. Jin, M. P. Scott, M. V. Nachury, E. T. Spiliotis, W. J. Nelson, A septin diffusion barrier at the base of the primary cilium maintains ciliary membrane protein distribution. Science 329, 436–439 (2010). [Abstract] [Full Text]