Cell Cycle-Related Kinase (CCRK) regulates ciliogenesis and Hedgehog signaling in mice

Abstract

The Hedgehog (Hh) signaling pathway plays a key role in cell fate specification, proliferation, and survival during mammalian development. Cells require a small organelle, the primary cilium, to respond properly to Hh signals and the key regulators of Hh signal transduction exhibit dynamic localization to this organelle when the pathway is activated. Here, we investigate the role of Cell Cycle Related kinase (CCRK) in regulation of cilium-dependent Hh signaling in the mouse. Mice mutant for Ccrk exhibit a variety of developmental defects indicative of inappropriate regulation of this pathway. Cell biological, biochemical and genetic analyses indicate that CCRK is required to control the Hedgehog pathway at the level or downstream of Smoothened and upstream of the Gli transcription factors, Gli2 and Gli3. In vitro experiments indicate that Ccrk mutant cells show a greater deficit in response to signaling over long time periods than over short ones. Similar to Chlamydomonas mutants lacking the CCRK homolog, LF2, mouse Ccrk mutant cells show defective regulation of ciliary length and morphology. Ccrk mutant cells exhibit defects in intraflagellar transport (the transport mechanism used to assemble cilia), as well as slowed kinetics of ciliary enrichment of key Hh pathway regulators. Collectively, the data suggest that CCRK positively regulates the kinetics by which ciliary proteins such as Smoothened and Gli2 are imported into the cilium, and that the efficiency of ciliary recruitment allows for potent responses to Hedgehog signaling over long time periods.

LF4/MOK and a CDK-related kinase regulate the number and length of cilia inTetrahymena

“…The Tetrahymena cells lacking either LF4A or its activator, CDKR1 (see below), have longer but also fewer locomotory cilia. In the mouse, a loss of ICK or its activator CCRK, in different cell types leads to either longer or shorter cilia [5, 42, 93]. Importantly, in Chlamydomonas, hypomorphic LF2 alleles confer longer cilia, but a null allele produces variable length (including shorter) cilia and inability to regenerate cilia after deciliation [47, 64, 94].…”

The kinases male germ cell‐associated kinase and cell cycle‐related kinase regulate kinesin‐2 motility in Caenorhabditis elegans neuronal cilia

“…This phenotype is consistent with the findings in Chlamydomonas lf2 mutant flagella and cilia of mammalian cells in which ccrk is knocked down. 23,25,29,30 However, in the dye-filling assay, all dyf-18 mutants showed a subtle Dyf phenotype.…”

“…The Chlamydomonas kinesin‐II motor subunit FLA8/KIF3B is phosphorylated and inactivated by the calcium‐dependent kinase CDPK1, which inhibits IFT entry probably by disrupting the interactions between kinesin‐II and IFT particles . Other kinases, including cell cycle‐related kinase (CCRK), ros‐cross hybridizing kinase (RCK) family members (MAK, ICK and MOK) and their homologs in Chlamydomonas , C. elegans and other species, have been implicated in the inhibition of kinesin‐II due to the long‐cilia phenotypes in their absence . MAK and ICK are substrates of CCRK .…”

“…19 Other kinases, including cell cycle-related kinase (CCRK), ros-cross hybridizing kinase (RCK) family members (MAK, ICK and MOK) and their homologs in Chlamydomonas, C. elegans and other species, have been implicated in the inhibition of kinesin-II due to the long-cilia phenotypes in their absence. [20][21][22][23][24][25][26][27][28][29][30] MAK and ICK are substrates of CCRK. 23,31,32 ICK is reported to phosphorylate the mammalian kinesin-II motor subunit KIF3A.…”

How the Ciliary Membrane Is Organized Inside-Out to Communicate Outside-In

“…Cyclin-dependent kinase 20 ( Cdk20 , also known as Ccrk ) mutant mice display neuroepithelial cilia that are swollen and short [59]. Cdk20 mutant mouse embryonic fibroblasts have attenuated Hedgehog signaling, reflected by reduced ciliary SMO upon pathway activation [59]. The role of CDK20 in controlling ciliary length and morphology is highly conserved across diverse species, as mutants in LF2 , a C. reinhardtii homolog of Cdk20 , also display bulbous cilia [60].…”