title: DLK-1/p38 MAP Kinase Signaling Controls Cilium Length by Regulating RAB-5 Mediated Endocytosis in Caenorhabditis elegans.
abstract: Cilia are sensory organelles present on almost all vertebrate cells. Cilium length is constant, but varies between cell types, indicating that cilium length is regulated. How this is achieved is unclear, but protein transport in cilia (intraflagellar transport, IFT) plays an important role. Several studies indicate that cilium length and function can be modulated by environmental cues. As a model, we study a C. elegans mutant that carries a dominant active G protein α subunit (gpa-3QL), resulting in altered IFT and short cilia. In a screen for suppressors of the gpa-3QL short cilium phenotype, we identified uev-3, which encodes an E2 ubiquitin-conjugating enzyme variant that acts in a MAP kinase pathway. Mutation of two other components of this pathway, dual leucine zipper-bearing MAPKKK DLK-1 and p38 MAPK PMK-3, also suppress the gpa-3QL short cilium phenotype. However, this suppression seems not to be caused by changes in IFT. The DLK-1/p38 pathway regulates several processes, including microtubule stability and endocytosis. We found that reducing endocytosis by mutating rabx-5 or rme-6, RAB-5 GEFs, or the clathrin heavy chain, suppresses gpa-3QL. In addition, gpa-3QL animals showed reduced levels of two GFP-tagged proteins involved in endocytosis, RAB-5 and DPY-23, whereas pmk-3 mutant animals showed accumulation of GFP-tagged RAB-5. Together our results reveal a new role for the DLK-1/p38 MAPK pathway in control of cilium length by regulating RAB-5 mediated endocytosis.
authors.affiliation: Department of Cell Biology, Erasmus MC, Rotterdam, the Netherlands.
authors.forename: Aniek
authors.initials: A
authors.lastname: van der Vaart
authors.affiliation: Department of Cell Biology, Erasmus MC, Rotterdam, the Netherlands.
authors.forename: Suzanne
authors.initials: S
authors.lastname: Rademakers
authors.affiliation: Department of Cell Biology, Erasmus MC, Rotterdam, the Netherlands.
authors.forename: Gert
authors.initials: G
authors.lastname: Jansen
mesh_terms: D000818:Animals; D017173:Caenorhabditis elegans / Q000166:cytology / Q000235:genetics / Q000378:metabolism*; D029742:Caenorhabditis elegans Proteins / Q000235:genetics / Q000378:metabolism*; D002923:Cilia / Q000378:metabolism; D004705:Endocytosis; D019206:GTP-Binding Protein alpha Subunits, Gi-Go / Q000235:genetics / Q000378:metabolism*; D020662:Guanine Nucleotide Exchange Factors / Q000235:genetics / Q000378:metabolism*; D020930:MAP Kinase Kinase Kinases / Q000235:genetics / Q000378:metabolism*; D020935:MAP Kinase Signaling System; D020928:Mitogen-Activated Protein Kinases / Q000235:genetics / Q000378:metabolism
chemical_list: D029742:Caenorhabditis elegans Proteins; D020662:Guanine Nucleotide Exchange Factors; C575474:RABX-5 protein, C elegans; C502292:RME-6 protein, C elegans; C501263:gpa-3 protein, C elegans; D020928:Mitogen-Activated Protein Kinases; C445124:pmk-3 protein, C elegans; C498050:DLK-1 protein, C elegans; D020930:MAP Kinase Kinase Kinases; D019206:GTP-Binding Protein alpha Subunits, Gi-Go