Evidence for a role of the ciliopathy protein MKS1 in plasma membrane-actin
interaction
C. Campillo1, C.R. Fisch2, J. Jerber2, B. Desforges2, L. Combettes3, M. ColladoHilly3, N. Lebreton2 , P. Nassoy1, C. Sykes1, P. Dupuis-Williams2,3,4
1Laboratoire
2ATIGE
Genopole®« Centrioles and Associated Pathologies» 91025, Evry, France,
3UMR-S757
3Ecole
PCC Institut Curie / CNRS UMR 168 / Université Paris 6, 75231 Paris Cedex 05, France
INSERM, Université Paris Sud, 91400 ORSAY, France
Supérieure de Physique et de Chimie Industrielles, 75005, Paris, France
Mutations in the protein MKS1 cause severe developmental disorders including
Bardet-Biedl (BBS) and Meckel-Gruber syndromes (MKS). Those genetic diseases
which typically display pleiotropic clinical features such as cystic kidneys and livers,
polydactyly and defective development of the central nervous system result from cilia
dysfunction and belong to the growing list of ciliopathies. Dysfunctional MKS1
caused a panel of cellular defects ranging from abortive centriolar migration to ciliary
instability and defective ciliary signaling (Dawe et al., 2007; Bialas et al., 2009;
Tammachote et al., 2009). Most analysis converge to the conclusion that in
vertebrates, the depletion of MKS1 leads to Meckel Gruber Syndrome (or MKS-like
in the mouse) and to impairment of Hh signaling pathways (Breunig et al., 2008;
Weatherbee et al., 2009; Cui et al., 2011; Dowdle et al., 2011; Zhao and Malicki,
2011). Accordingly, MKS1 has been shown to be localized at the transition zone (TZ,
which corresponds to the boundary between ciliary and plasma membranes) and as
such, involved in the ciliary membrane composition (Cui et al., 2011; Chi et al, 2011).
By combining two complementary cell models –a mammalian epithelial cell line and
the unicellular Paramecium, we identified a pre-ciliary function of MKS1 that provides
a unifying mechanism of the ciliary phenotypes observed. We show that MKS1
displays a typical pattern of membrane-associated protein, being localised to
exocytotic vesicles, the plasma and the ciliary membrane and to cell junctions during
epithelial differentiation. Based on RNAi experiments of MKS1 which leads to
impairment of ciliary sensory functions, defective vesicle transport and plasma
membrane distension, we propose that MKS1 knockdown impairs interactions
between actin and membranes. This hypothesis is presently tested by biophysical
approaches by measuring with micropipette aspiration and membrane nanotube
extrusion the strength of the association between cortical cytoskeleton and the
plasma membrane.