IndraLab

"The Q607R mutant also up-regulated USP13 phosphorylation at Y708 ( xref Bii)."

"Further analysis found that tacrine hydrochloride significantly decreased CLK3-Q607R–enhanced purine production and USP13-Y708 phosphorylation in CCA cells ( xref )."

"Similar data were also observed in the EGF-induced increase in CLK3 expression, USP13 phosphorylation at Y708, and proliferation in CCA cells ( xref )."

"We demonstrated that (1) a recurrent Q607R somatic substitution in CLK3 was identified in 8% of 100 human CCAs, particularly in patients with CCA metastasis; (2) the expression of CLK3 was significantly up-regulated in CCA compared with matched control tissues; (3) CLK3 knockdown significantly inhibited CCA aggressiveness in vitro and in vivo; (4) gene ontology term enrichment and MS assays indicated that high CLK3 expression in CCA patients mainly regulated nucleotide metabolism, especially purine biosynthesis; (5) mechanistically, CLK3 directly phosphorylated USP13 at Y708, which promoted its binding to c-Myc, a critical purine synthesis–associated transcription factor, thereby preventing Fbxl14-mediated c-Myc ubiquitination and activating the transcription of purine metabolic genes; (6) the CCA-associated CLK3-Q607R mutant induced USP13-Y708 phosphorylation and enhanced the activity of c-Myc; (7) in turn, c-Myc transcriptionally up-regulated CLK3; (8) importantly, levels of CLK3 significantly correlated with the expression of phospho-USP13-Y708, c-Myc, and ATIC in human CCA specimens; and (9) tacrine hydrochloride was identified as a potential compound to inhibit the aberrant CLK3-enhanced CCA invasiveness."

"Thus, CLK3-mediated phosphorylation of USP13 at Tyr708 promotes cholangiocarcinoma progression by activating c-Myc-induced purine synthesis, providing a new and viable therapeutic target for the treatment of cholangiocarcinoma associated with CLK3 mutations ( xref )."

"Aurora B and ataxia telangiectasia mutated (ATM) regulate the expression of USP13 via phosphorylation of USP13 at Ser114 and Thr196 to promote the interaction between them, respectively, while the CDC-like kinase 3 (CLK3)-Q607R mutation induces the phosphorylation of USP13 at Tyr708 and promotes its association with c-Myc ( xref )."

"USP13 stabilizes its substrate, and at the same time, the activity of USP13 is upregulated by CLK3 via promoting phosphorylation of USP13 at Tyr708, which increases its deubiquitinating enzyme activity."

"Notably, the CCA-associated CLK3-Q607R mutant induced USP13-Y708 phosphorylation and enhanced the activity of c-Myc."

"CLK3-mediated phosphorylation of USP13 at Tyr708 promotes cholangiocarcinoma progression by activating c-Myc-induced purine synthesis, providing a new and viable therapeutic target for treating cholangiocarcinoma associated with CLK3 mutations [ xref ]."

"In cholangiocarcinoma, TGF-β signaling triggers the phosphorylation of CLK3, a serine/threonine kinase that directly phosphorylates USP13 at Y708 and facilitates USP13 interaction with c-Myc ( xref ); in GSCs, USP13 can enhance the stability through deubiquitinating c-Myc, activating purine synthesis mediated by c-Myc and inducing the tumorigenesis of GSCs ( xref ); in hepatocellular carcinoma, knockdown of USP13 by shRNA can markedly downregulate c-Myc expression, resisting xenograft tumor growth of HCC ( xref )."

"CLK3 was found to be upregulated in cholangiocarcinoma (CCA) patients and plays a role in nucleotide metabolism. xref Meanwhile, a gain of function somatic mutation Q607R was identified in CLK3 kinase domain, which induced USP13 Y708 phosphorylation and promoted USP13 binding to c-Myc."

"We made a special antibody against USP13-Y708 phosphorylation for the following experiments."

"Furthermore, CLK3-induced phosphorylation of the Tyr708 residue in USP13 promotes cholangiocarcinoma progression by activating c-Myc-mediated purine synthesis ( xref )."

"CLK3 mediated the phosphorylation of USP13 at Y708, promoting its binding to c-Myc, which is an important transcription factor and also known as an oncogene in many cancers [ xref ]."

"Moreover, phosphorylation of USP13 at Y708 by CDC-like kinase 3 (CLK3) can facilitate the interaction between USP13 and the proto-oncoprotein c-Myc, further suppressing tumorigenesis ( xref )."

"As expected, USP13-Y708E transfection in HEK293 cells significantly inhibited the binding of c-Myc to Fbxl14, while USP13-Y708F significantly increased it (data not shown), revealing that USP13 phosphorylation at Y708 reverts c-Myc ubiquitination mediated by Fbxl14, thereby enhancing its stability ( xref )."