Polycystin-1 Regulates Actomyosin Contraction and the Cellular Response to Extracellular Stiffness

Elisa Agnese Nigro,Angela Bachi,Maddalena Castelli,Alessandra Boletta,Vittoria Matafora,Angela Pesenti Gritti,Gianfranco Distefano,Marco Chiaravalli

doi:10.1038/s41598-019-53061-0

Abstract

Polycystin-1 (PC-1) and 2 (PC-2) are the products of the PKD1 and PKD2 genes, which are mutated in Autosomal Dominant Polycystic Kidney Disease (ADPKD). They form a receptor/channel complex that has been suggested to function as a mechanosensor, possibly activated by ciliary bending in the renal tubule, and resulting in calcium influx. This model has recently been challenged, leaving the question as to which mechanical stimuli activate the polycystins still open. Here, we used a SILAC/Mass-Spec approach to identify intracellular binding partners of tagged-endogenous PC-1 whereby we detected a class of interactors mediating regulation of cellular actomyosin contraction. Accordingly, using gain and loss-of-function cellular systems we found that PC-1 negatively regulates cellular contraction and YAP activation in response to extracellular stiffness. Thus, PC-1 enables cells to sense the rigidity of the extracellular milieu and to respond appropriately. Of note, in an orthologous murine model of PKD we found evidence of increased actomyosin contraction, leading to enhanced YAP nuclear translocation and transcriptional activity. Finally, we show that inhibition of ROCK-dependent actomyosin contraction by Fasudil reversed YAP activation and significantly improved disease progression, in line with recent studies. Our data suggest a possible direct role of PC-1 as a mechanosensor of extracellular stiffness.

Highlights

Autosomal Dominant Polycystic Kidney Disease (ADPKD) is a relatively common monogenic disorder, affecting approximately 1:2000 individuals[1,2]
The mass-spectrometry analysis of mouse embryonic fibroblasts carrying tagged endogenous PC-1 revealed that PC-1 interacts with proteins that regulate the actomyosin contraction machinery
We further found increased phosphorylation state of myosin light chain (pMLC) in polycystic kidneys generated by kidney-specific inactivation of Pkd[1]

Summary

Introduction

Autosomal Dominant Polycystic Kidney Disease (ADPKD) is a relatively common monogenic disorder, affecting approximately 1:2000 individuals[1,2]. The mechanism of activation of this receptor/channel complex remains unclear Chemical stimuli such as Extracellular Matrix (ECM) components and Wnt proteins have been shown to interact with PC-1 and to mediate its activation[18], highlighting the possibility of this receptor being regulated by specific chemical ligands. A recent study suggests that PC-1 has a role in regulating osteoblastogenesis and adipogenesis through interaction with the transcriptional coactivator with PDZ-binding motif (TAZ)[29,36] Mechanical forces, such as ECM stiffness activate the PC-1/PC-2 complex leading to induction of PC-1- C-Terminal Tail (PC-1-CTT) cleavage and TAZ nuclear translocation to enhance osteoblast gene transcription and to inhibit PPARγ and adipogenesis. Our data seem to suggest that the physical properties of the extracellular milieau, rather than its chemical composition, might play a key role in regulating the PC-1 receptor function, opening a new perspective on the mechanosensory activity of this receptor and the potential mechanism of pathogenesis

Methods

Results

Conclusion