CSPP-L and EB3 localize to centriolar satellites and are required for satellite-dependent recruitment of ciliopathy proteins to the centrosome
© Sternemalm et al. 2015
Published: 13 July 2015
Centrosome/Spindle Pole associated Protein 1 (CSPP1, JBTS21) mutations cause Joubert syndrome (JBTS) and JBTS-related ciliopathies. The large protein isoform CSPP-L is a ciliary protein required for ciliogenesis and stabilization of the ciliopathy protein RPGRIP1L (NPHP8/JBTS7/MKS5/FTM) at the ciliary transition zone (TZ). However, RPGRIP1L is dispensable for ciliogenesis and the mechanism by which CSPP-L promotes ciliogenesis is unclear.
We applied immunogold electron, immunofluorescence and fluorescence live cell microscopy to determine localization of CSPP-L at high spatial and temporal resolution. We elucidated the functional interplay of CSPP-L with centriolar satellites in hTERT-RPE1 and HeLa cells using biochemical analysis of CSPP-L complexes, siRNA modulated gene expression and quantitative immunofluoresecence microscopy.
We show that CSPP-L localizes to centriolar satellites, in addition to axonemal microtubule (MT) plus ends and the TZ, and that the MT plus end-tracking protein EB3 also localizes to satellites. CSPP-L complexed with the known satellite component PCM1 and GFP-CSPP-L showed satellite-like dynamics. Importantly, CSPP-L depletion decreased formation of PCM1, CEP290 and EB3-comprising satellites, whereas depletion or inactivation of EB3 impaired centrosomal localization of CSPP-L.
Our results identify a new link between MT plus ends and centriolar satellites, and suggest that CSPP-L contributes to ciliogenesis by promoting EB3- and dynein-dependent recruitment of satellite components to the centrosome.
This article is published under license to BioMed Central Ltd. This is an Open Access article distributed under the terms of the Creative Commons Attribution License (http://creativecommons.org/licenses/by/4.0), which permits unrestricted use, distribution, and reproduction in any medium, provided the original work is properly cited. The Creative Commons Public Domain Dedication waiver (http://creativecommons.org/publicdomain/zero/1.0/) applies to the data made available in this article, unless otherwise stated.