The Ciliopathy Protein CC2D2A Associates with NINL and Functions in RAB8-MICAL3-Regulated Vesicle Trafficking.
Ciliopathies are a group of human disorders caused by dysfunction of primary cilia, ubiquitous microtubule-based organelles involved in transduction of extra-cellular signals to the cell. This function requires the concentration of receptors and channels in the ciliary membrane, which is achieved by complex trafficking mechanisms, in part controlled by the small GTPase RAB8, and by sorting at the transition zone located at the entrance of the ciliary compartment. Mutations in the transition zone gene CC2D2A cause the related Joubert and Meckel syndromes, two typical ciliopathies characterized by central nervous system malformations, and result in loss of ciliary localization of multiple proteins in various models. The precise mechanisms by which CC2D2A and other transition zone proteins control protein entrance into the cilium and how they are linked to vesicular trafficking of incoming cargo remain largely unknown. In this work, we identify the centrosomal protein NINL as a physical interaction partner of CC2D2A. NINL partially co-localizes with CC2D2A at the base of cilia and ninl knockdown in zebrafish leads to photoreceptor outer segment loss, mislocalization of opsins and vesicle accumulation, similar to cc2d2a-/- phenotypes. Moreover, partial ninl knockdown in cc2d2a-/- embryos enhances the retinal phenotype of the mutants, indicating a genetic interaction in vivo, for which an illustration is found in patients from a Joubert Syndrome cohort. Similar to zebrafish cc2d2a mutants, ninl morphants display altered Rab8a localization. Further exploration of the NINL-associated interactome identifies MICAL3, a protein known to interact with Rab8 and to play an important role in vesicle docking and fusion. Together, these data support a model where CC2D2A associates with NINL to provide a docking point for cilia-directed cargo vesicles, suggesting a mechanism by which transition zone proteins can control the protein content of the ciliary compartment.
Institute for Molecular Life Sciences, University of Zurich, Zurich, Switzerland; Institute of Medical Genetics, University of Zurich, Zurich, Switzerland.
Ruxandra
R
Bachmann-Gagescu
Department of Otorhinolaryngology, Radboud University Medical Centre, Nijmegen, the Netherlands; Radboud Institute for Molecular Life Sciences, Radboud University Nijmegen, the Netherlands.
Margo
M
Dona
Department of Otorhinolaryngology, Radboud University Medical Centre, Nijmegen, the Netherlands; Radboud Institute for Molecular Life Sciences, Radboud University Nijmegen, the Netherlands.
Lisette
L
Hetterschijt
Department of Otorhinolaryngology, Radboud University Medical Centre, Nijmegen, the Netherlands.
Edith
E
Tonnaer
Department of Otorhinolaryngology, Radboud University Medical Centre, Nijmegen, the Netherlands.
Theo
T
Peters
Department of Otorhinolaryngology, Radboud University Medical Centre, Nijmegen, the Netherlands; Radboud Institute for Molecular Life Sciences, Radboud University Nijmegen, the Netherlands.
Erik
E
de Vrieze
Radboud Institute for Molecular Life Sciences, Radboud University Nijmegen, the Netherlands; Department of Human Genetics, Radboud University Medical Centre, Nijmegen, the Netherlands.
Dorus A
DA
Mans
Radboud Institute for Molecular Life Sciences, Radboud University Nijmegen, the Netherlands; Department of Human Genetics, Radboud University Medical Centre, Nijmegen, the Netherlands.
Sylvia E C
SE
van Beersum
Department of Pediatrics, University of Washington, Seattle, Washington, United States of America.
Ian G
IG
Phelps
Radboud Institute for Molecular Life Sciences, Radboud University Nijmegen, the Netherlands; Department of Human Genetics, Radboud University Medical Centre, Nijmegen, the Netherlands; Department of Biochemistry, University of Western Ontario, London, Ontario, Canada.
Heleen H
HH
Arts
Department of Ophthalmology, Radboud University Medical Centre, Nijmegen, the Netherlands.
Jan E
JE
Keunen
Division of Experimental Ophthalmology and Medical Proteome Center, Centre for Ophthalmology, Eberhard Karls University Tuebingen, Germany.
Marius
M
Ueffing
Radboud Institute for Molecular Life Sciences, Radboud University Nijmegen, the Netherlands; Department of Human Genetics, Radboud University Medical Centre, Nijmegen, the Netherlands.
Ronald
R
Roepman
Division of Experimental Ophthalmology and Medical Proteome Center, Centre for Ophthalmology, Eberhard Karls University Tuebingen, Germany.
Karsten
K
Boldt
Department of Pediatrics, University of Washington, Seattle, Washington, United States of America.
Dan
D
Doherty
Fred Hutchinson Cancer Research Center, Seattle, Washington, United States of America.
Cecilia B
CB
Moens
Institute for Molecular Life Sciences, University of Zurich, Zurich, Switzerland.
Stephan C F
SC
Neuhauss
Department of Otorhinolaryngology, Radboud University Medical Centre, Nijmegen, the Netherlands; Radboud Institute for Molecular Life Sciences, Radboud University Nijmegen, the Netherlands; Department of Human Genetics, Radboud University Medical Centre, Nijmegen, the Netherlands.
Hannie
H
Kremer
Department of Otorhinolaryngology, Radboud University Medical Centre, Nijmegen, the Netherlands; Radboud Institute for Molecular Life Sciences, Radboud University Nijmegen, the Netherlands.
Erwin
E
van Wijk
D000015:Abnormalities, Multiple / Q000235:genetics / Q000378:metabolism / Q000473:pathology; D000818:Animals; D002531:Cerebellum / Q000002:abnormalities* / Q000378:metabolism / Q000473:pathology; D002923:Cilia / Q000235:genetics / Q000378:metabolism / Q000473:pathology; D002925:Ciliary Motility Disorders / Q000235:genetics* / Q000378:metabolism / Q000473:pathology; D003598:Cytoskeletal Proteins; D004677:Encephalocele / Q000235:genetics* / Q000378:metabolism / Q000473:pathology; D005124:Eye Abnormalities / Q000235:genetics / Q000378:metabolism / Q000473:pathology; D055785:Gene Knockdown Techniques; D006801:Humans; D052177:Kidney Diseases, Cystic / Q000235:genetics / Q000378:metabolism / Q000473:pathology; D008869:Microtubule-Associated Proteins / Q000235:genetics / Q000378:metabolism*; D006899:Mixed Function Oxygenases / Q000235:genetics* / Q000378:metabolism; D009154:Mutation; D009687:Nuclear Proteins / Q000235:genetics / Q000378:metabolism*; D007690:Polycystic Kidney Diseases / Q000235:genetics* / Q000378:metabolism / Q000473:pathology; D021381:Protein Transport / Q000235:genetics; D011506:Proteins / Q000235:genetics* / Q000378:metabolism; D012160:Retina / Q000002:abnormalities* / Q000378:metabolism / Q000473:pathology; D012174:Retinitis Pigmentosa; D015398:Signal Transduction; D015027:Zebrafish; D020691:rab GTP-Binding Proteins / Q000235:genetics* / Q000378:metabolism
C528701:CC2D2A protein, human; D003598:Cytoskeletal Proteins; D008869:Microtubule-Associated Proteins; C476755:NINL protein, human; D009687:Nuclear Proteins; D011506:Proteins; C561623:MICAL3 protein, human; D006899:Mixed Function Oxygenases; C082377:RAB8A protein, human; D020691:rab GTP-Binding Proteins