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Primary cilia are hair-like organelles that play crucial roles in vertebrate development, organogenesis and when dysfunctional result in pleiotropic human genetic disorders called ciliopathies, characterized by overlapping phenotypes, such as renal and hepatic cysts, skeletal defects, retinal degeneration and central nervous system malformations. Primary cilia act as communication hubs to transfer extracellular signals into intracellular responses and are essential for Hedgehog (Hh) signal transduction in mammals. Despite the renewed interest in this ancient organelle of growing biomedical importance, the molecular mechanisms that trigger cilia formation, extension and ciliary signal transduction are still not fully understood. Here we provide, for the first time, evidence that the deubiquitinase ubiquitin-specific protease-14 (Usp14), a major regulator of the ubiquitin proteasome system (UPS), controls ciliogenesis, cilia elongation and Hh signal transduction. Moreover, we show that pharmacological inhibition of Usp14 positively affects Hh signal transduction in a model of autosomal dominant polycystic kidney disease. These findings provide new insight into the spectrum of action of UPS in cilia biology and may provide novel opportunities for therapeutic intervention in human conditions associated with ciliary dysfunction.

MicroRNAs (miRNAs) are attractive therapeutic targets and promising candidates as molecular biomarkers for various therapy-resistant tumors. However, the association between miRNAs and drug resistance in melanoma remains to be elucidated. We used an integrative genomic analysis to comprehensively study the miRNA expression profiles of drug-resistant melanoma patients and cell lines. MicroRNA-181a and -181b (miR181a/b) were identified as the most significantly down-regulated miRNAs in resistant melanoma patients and cell lines. Re-establishment of miR-181a/b expression reverses the resistance of melanoma cells to the BRAF inhibitor dabrafenib. Introduction of miR-181 mimics markedly decreases the expression of TFAM in A375 melanoma cells resistant to BRAF inhibitors. Furthermore, melanoma growth was inhibited in A375 and M14 resistant melanoma cells transfected with miR-181a/b mimics, while miR-181a/b depletion enhanced resistance in sensitive cell lines. Collectively, our study demonstrated that miR-181a/b could reverse the resistance to BRAF inhibitors in dabrafenib resistant melanoma cell lines. In addition, miR-181a and -181b are strongly down-regulated in tumor samples from patients before and after the development of resistance to targeted therapies. Finally, melanoma tissues with high miR-181a and -181b expression presented favorable outcomes in terms of Progression Free Survival, suggesting that miR-181 is a clinically relevant candidate for therapeutic development or biomarker-based therapy selection.

Cilia are critical mediators of paracrine signaling; however, it is unknown whether proteins that contribute to ciliopathies converge on multiple paracrine pathways through a common mechanism. Here, we show that loss of cilopathy-associated proteins Bardet-Biedl syndrome 4 (BBS4) or oral-facial-digital syndrome 1 (OFD1) results in the accumulation of signaling mediators normally targeted for proteasomal degradation. In WT cells, several BBS proteins and OFD1 interacted with proteasomal subunits, and loss of either BBS4 or OFD1 led to depletion of multiple subunits from the centrosomal proteasome. Furthermore, overexpression of proteasomal regulatory components or treatment with proteasomal activators sulforaphan'e (SFN) and mevalonolactone (MVA) ameliorated signaling defects in cells lacking BBS1, BBS4, and OFD1, in morphant zebrafish embryos, and in induced neurons from Ofd1-deficient mice. Finally, we tested the hypothesis that other proteasome-dependent pathways not known to be associated with ciliopathies are defective in the absence of ciliopathy proteins. We found that loss of BBS1, BBS4, or OFD1 led to decreased NE-kappa B activity and concomitant I kappa B beta accumulation and that these defects were ameliorated with SFN treatment. Taken together, our data indicate that basal body proteasomal regulation governs paracrine signaling pathways and suggest that augmenting proteasomal function might benefit ciliopathy patients.