Submitted on March 3, 2009
Revised on April 15, 2009
Accepted on April 15, 2009
Regulation of primary cilia formation by ceramide
Guanghu Wang, Kannan Krishnamurthy, and Erhard Bieberich
Medical College of Georgia, Augusta, GA 30912
Corresponding Author: ebieberich{at}mcg.edu
The primary cilium is an important sensory organelle the regulation of which is not fully understood. We found that in polarized Madin-Darby Canine Kidney (MDCK) cells, the sphingolipid ceramide is specifically distributed to a cis-Golgi compartment at the base of the primary cilium. This compartment immunostained for the centrosome marker -tubulin, the Rho type GTPase Cdc42, and atypical protein kinase C/ (aPKC), a kinase activated by ceramide and associated with a polarity protein complex consisting of Par6 and Cdc42. Inhibition of ceramide biosynthesis with Fumonisin B1 prevented co-distribution of aPKC and Cdc42 in the centrosomal/pericentriolar compartment and severely impaired ciliogenesis. Cilium formation and co-distribution of aPKC and Cdc42 were restored by incubation with N-acetyl or N-palmitoyl sphingosine (C2 or C16 ceramide), or the ceramide analog N-oleoyl serinol (S18). Cilium formation was also restored by the GSK-3ß inhibitor indirubin-3-monoxime, suggesting that regulation of ciliogenesis depends on the inhibition of GSK-3ß by ceramide-activated aPKC. Consistently, inhibition of aPKC with a pseudosubstrate inhibitor prevented restoration of ciliogenesis by C2 ceramide or S18. Our data show for the first time that ceramide is required for primary cilium formation.
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