Abstract

Centriolar satellites (CS) are small proteinaceous granules that cluster around the centrosome and serve as cargo vehicles for centrosomal proteins. It is generally accepted that CS support a number of canonical and specialized centrosome functions. Consequently, these highly dynamic structures are the target of regulation by several cellular signalling pathways. Two decades of research have led to the identification of a large number of molecular components and new biological roles of CS. Here, we summarize the latest advances in the continuous efforts to uncover the compositional, functional, dynamic and regulatory aspects of CS. We also report on our discovery that osmotic stress conditions render CS immobile and insensitive to remodelling. Upon a range of p38-activating stimuli, MK2 phosphorylates the CS component CEP131, resulting in 14-3-3 binding and a block to CS formation. This normally manifests as a rapid cellular depletion of satellites. In the case of osmotic stress, a potent inducer of p38 activity, CS translocation and dissolution is blocked, with the net result that satellites persist in an immobile state directly adjacent to the centrosome. Our results highlight a unique scenario where p38 activation and CS depletion is uncoupled, with potential implications for physiological and pathological osmotic stress responses.

Highlights

  • Centriolar satellites (CS) are small, microscopically visible, proteinaceous granules that gravitate around the centrosome (Figure 1A,B) [1,2,3,4]

  • Osmotic and to some degree oxidative stress did not result in the loss of CS as judged by widefield fluorescence microscopy of CEP131 and PCM1 immunostainings (Figure 3B–D)

  • P38by byosmotic osmoticstress stressagents agentsisisnot not accompanied by depletion, we considered the possibility that loss requires an accompanied by CS depletion, we considered the possibility that CS loss requires anadditional additional signalling pathway that that is notisactivated after osmotic stress

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Summary

Introduction

Centriolar satellites (CS) are small, microscopically visible, proteinaceous granules that gravitate around the centrosome (Figure 1A,B) [1,2,3,4]. After more than two decades of research it has become clear that CS are functionally and spatially linked to the centrosome and contain many proteins which are found to localize to the centriolar and pericentriolar regions as well as the ciliary transition zone [5,6,7,8]. CS are linked to the microtubule network by motor proteins, which promote their movement towards or away from the centrosome [2,9,10,11]. As CS contain numerous structural and regulatory centrosomal components, they are ideally positioned to communicate perturbations or cell-cycle status to the centrosome. Their molecular function with regard to canonical and specialized centrosome functions has formed the basis of numerous studies

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