AMPK Phosphorylates ZDHHC13 to Increase MC1R Activity and Suppress Melanomagenesis.

Inherited genetic variations in the melanocortin-1 receptor (MC1R) responsible for human red hair color (RHC) variants are associated with impaired DNA damage repair and increased melanoma risk. MC1R signaling is critically dependent on palmitoylation, primarily mediated by the protein acyltransferase zinc finger DHHC-type palmitoyltransferase 13 (ZDHHC13). A better understanding of how ZDHHC13 is physiologically activated could help identify approaches to prevent melanomagenesis in redheads. Here, we report that AMP-activated protein kinase (AMPK) phosphorylates ZDHHC13 at S208 to strengthen the interaction between ZDHHC13 and MC1R-RHC, leading to enhanced MC1R palmitoylation in redheads. Consequently, phosphorylation of ZDHHC13 by AMPK increased MC1R-RHC downstream signaling. AMPK activation and MC1R palmitoylation repressed UVB-induced transformation of human melanocytes in vitro and delayed melanomagenesis in vivo in C57BL/6J-MC1R-RHC mice. The importance of AMPK to MC1R signaling was validated in human melanomas where AMPK upregulation correlated with expression of factors downstream from MC1R signaling and with prolonged patient survival. These findings suggest AMPK activation as a promising strategy to reduce melanoma risk, especially for individuals with red hair. SIGNIFICANCE: Phosphorylation of ZDHHC13 by AMPK at S208 promotes MC1R activation and suppresses melanocyte transformation, indicating activation of AMPK as a potential approach to prevent melanoma in people with red hair.

PYK2 Is Involved in Premalignant Acinar Cell Reprogramming and Pancreatic Ductal Adenocarcinoma Maintenance by Phosphorylating ß-CateninY654.

BACKGROUND & AIMS: Identification and validation of new functionally relevant and pharmacologically actionable targets for pancreatic ductal adenocarcinoma (PDAC) remains a great challenge. Premalignant acinar cell reprogramming (acinar-to-ductal metaplasia [ADM]) is a precursor of pancreatic intraepithelial neoplasia (PanIN) lesions that can progress to PDAC. This study investigated the role of proline-rich tyrosine kinase 2 (PYK2) in mutant Kras-induced and pancreatitis-associated ADM and PanIN formation, as well as in PDAC maintenance. METHODS: Genetically engineered mouse models of mutant Kras (glycine 12 to aspartic acid) and Pyk2 deletion were used for investigating the role of PYK2 in PDAC genesis in mice. In vitro ADM assays were conducted using primary pancreatic acinar cells isolated from mice. Immunohistochemistry, immunofluorescence, and a series of biochemical experiments were used to investigate upstream regulators/downstream targets of PYK2 in pancreatic carcinogenesis. PDAC cell line xenograft experiments were performed to study the role of PYK2 and its downstream target in PDAC maintenance. RESULTS: PYK2 was increased substantially in ADM lesions induced by mutant Kras or inflammatory injury. Pyk2 deletion remarkably suppressed ADM and PanIN formation in a mutant Kras-driven and pancreatitis-associated PDAC model, whereas PYK2 knockdown substantially inhibited PDAC cell growth in vitro and in nude mice. This study uncovered a novel yes-associated protein 1/transcriptional co-activator with PDZ binding motif/signal transducer and activator of transcription 3/PYK2/ß-catenin regulation axis in PDAC. Our results suggest that PYK2 contributes to PDAC genesis and maintenance by activating the Wnt/ß-catenin pathway through directly phosphorylating ß-cateninY654. CONCLUSIONS: The current study uncovers PYK2 as a novel downstream effector of mutant KRAS signaling, a previously unrecognized mediator of pancreatitis-induced ADM and a novel intervention target for PDAC.