Functional interactions between the ciliopathy-associated Meckel syndrome 1 (MKS1) protein and two novel MKS1-related (MKSR) proteins.
Meckel syndrome (MKS) is a ciliopathy characterized by encephalocele, cystic renal disease, liver fibrosis and polydactyly. An identifying feature of MKS1, one of six MKS-associated proteins, is the presence of a B9 domain of unknown function. Using phylogenetic analyses, we show that this domain occurs exclusively within a family of three proteins distributed widely in ciliated organisms. Consistent with a ciliary role, all Caenorhabditis elegans B9-domain-containing proteins, MKS-1 and MKS-1-related proteins 1 and 2 (MKSR-1, MKSR-2), localize to transition zones/basal bodies of sensory cilia. Their subcellular localization is largely co-dependent, pointing to a functional relationship between the proteins. This localization is evolutionarily conserved, because the human orthologues also localize to basal bodies, as well as cilia. As reported for MKS1, disrupting human MKSR1 or MKSR2 causes ciliogenesis defects. By contrast, single, double and triple C. elegans mks/mksr mutants do not display overt defects in ciliary structure, intraflagellar transport or chemosensation. However, we find genetic interactions between all double mks/mksr mutant combinations, manifesting as an increased lifespan phenotype, which is due to abnormal insulin-IGF-I signaling. Our findings therefore demonstrate functional interactions between a novel family of proteins associated with basal bodies or cilia, providing new insights into the molecular etiology of a pleiotropic human disorder.
Bialas
Nathan J
NJ
Department of Molecular Biology and Biochemistry, Simon Fraser University, Burnaby, BC V5A 1S6, Canada.
Inglis
Peter N
PN
Li
Chunmei
C
Robinson
Jon F
JF
Parker
Jeremy D K
JD
Healey
Michael P
MP
Davis
Erica E
EE
Inglis
Chrystal D
CD
Toivonen
Tiina
T
Cottell
David C
DC
Blacque
Oliver E
OE
Quarmby
Lynne M
LM
Katsanis
Nicholas
N
Leroux
Michel R
MR
D000595:Amino Acid Sequence; D000818:Animals; D017173:Caenorhabditis elegans / Q000235:genetics / Q000378:metabolism; D029742:Caenorhabditis elegans Proteins / Q000145:classification / Q000235:genetics / Q000378:metabolism*; D002923:Cilia / Q000378:metabolism / Q000473:pathology*; D019143:Evolution, Molecular; D006801:Humans; D008969:Molecular Sequence Data; D010641:Phenotype; D010802:Phylogeny; D011506:Proteins / Q000145:classification / Q000235:genetics / Q000378:metabolism*; D011993:Recombinant Fusion Proteins / Q000235:genetics / Q000378:metabolism; D016415:Sequence Alignment; D015398:Signal Transduction / Q000502:physiology
D029742:Caenorhabditis elegans Proteins; C509165:MKS1 protein, human; D011506:Proteins; D011993:Recombinant Fusion Proteins