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. Author manuscript; available in PMC: 2011 Aug 24.
Published in final edited form as: Exp Cell Res. 2009 Jul 2;315(16):2802–2817. doi: 10.1016/j.yexcr.2009.06.028

Figure 9. A model of primary cilia growth and elongation.

Figure 9

A. Primary cilia in an untreated cell. Primary cilia start to form after mitosis. During the early stage of G1 (or experimentally in G0 cells) primary cilia start to grow. With cell cycle progression (or with time increase in the quiescent state), cAMP and calcium concentrations increase. With participation of other factors (including cAMP-responsive GTP exchange protein or unknown factors, PKC and Aurora kinase) the increased cAMP and calcium levels prevent primary cilia from further growth. At this stage, there is equilibrium between growth and regression of primary cilia, balanced by all factors. B. Lithium and primary cilia. Addition of lithium to the cell culture causes inhibition of adenylate cyclase III, reducing cAMP and calcium levels. Lithium may also directly attenuate the intracellular calcium concentration. As a result, lithium disturbs the balance, favoring primary cilia to resume their growth.