AMPK Phosphorylates ZDHHC13 to Increase MC1R Activity and Suppress Melanomagenesis

Multicenter proteome-wide Mendelian randomization study identifies causal plasma proteins in melanoma and non-melanoma skin cancers

This study addresses the diagnostic and therapeutic challenges in malignant melanoma (MM) and non-melanoma skin cancers (NMSC). We aim to identify circulating proteins causally linked to MM and NMSC traits using a multicenter Mendelian randomization (MR) framework. We utilized large-scale cis-MR to estimate the impact of numerous plasma proteins on MM, NMSC, squamous cell carcinoma (SCC), and basal cell carcinoma (BCC). To ensure robustness, additional analyses like MR Steiger and Bayesian colocalization are conducted, followed by replication through meta-analytical methods. The associations between identified proteins and outcomes are also validated at the tissue level using Transcriptome-Wide Association Study methods. Furthermore, a protein-protein interaction analysis is conducted to explore the relationship between identified proteins and existing cancer medication targets. The MR analysis has identified associations of 13 plasma proteins with BCC, 2 with SCC, and 1 with MM. Specifically, ASIP and KRT5 are associated with BCC, with ASIP also potentially targeting MM. CTSS and TNFSF8 are identified as promising druggability candidates for BCC. This multidimensional approach nominates ASIP, KRT5, CTSS, and TNFSF8 as potential diagnostic and therapeutic targets for skin cancers.

Smad7 palmitoylation by the S-acyltransferase zDHHC17 enhances its inhibitory effect on TGF-β/Smad signaling

Intracellular signaling by the pleiotropic cytokine transforming growth factor-β (TGF-β) is inhibited by Smad7 in a feedback control mechanism. The activity of Smad7 is tightly regulated by multiple post-translational modifications. Using resin-assisted capture and metabolic labeling methods, we show here that Smad7 is S-palmitoylated in mammary epithelial cell models that are widely studied because of their strong responses to TGF-β and their biological relevance to mammary development and tumor progression. S-palmitoylation of Smad7 is mediated by zDHHC17, a member of a family of 23 S-acyltransferase enzymes. Moreover, we identified four cysteine residues (Cys202, Cys225, Cys415, and Cys417) in Smad7 as palmitoylation acceptor sites. S-palmitoylation of Smad7 on Cys415 and Cys417 promoted the translocation of Smad7 from the nucleus to the cytoplasm, enhanced the stability of the Smad7 protein, and enforced its inhibitory effect on TGF-β-induced Smad transcriptional response. Thus, our findings reveal a new post-translational modification of Smad7, and highlight an important role of S-palmitoylation to enhance inhibition of TGF-β/Smad signaling by Smad7.

ZDHHC20-mediated S-palmitoylation of YTHDF3 stabilizes MYC mRNA to promote pancreatic cancer progression

Post-translational modifications of proteins in malignant transformation and tumor maintenance of pancreatic ductal adenocarcinoma (PDAC) in the context of KRAS signaling remain poorly understood. Here, we use the KPC mouse model to examine the effect of palmitoylation on pancreatic cancer progression. ZDHHC20, upregulated by KRAS, is abnormally overexpressed and associated with poor prognosis in patients with pancreatic cancer. Dysregulation of ZDHHC20 promotes pancreatic cancer progression in a palmitoylation-dependent manner. ZDHHC20 inhibits the chaperone-mediated autophagic degradation of YTHDF3 through S-palmitoylation of Cys474, which can result in abnormal accumulation of the oncogenic product MYC and thereby promote the malignant phenotypes of cancer cells. Further, we design a biologically active YTHDF3-derived peptide to competitively inhibit YTHDF3 palmitoylation mediated by ZDHHC20, which in turn downregulates MYC expression and inhibits the progression of KRAS mutant pancreatic cancer. Thus, these findings highlight the therapeutic potential of targeting the ZDHHC20-YTHDF3-MYC signaling axis in pancreatic cancer.

Protein lipidation in health and disease: molecular basis, physiological function and pathological implication

Posttranslational modifications increase the complexity and functional diversity of proteins in response to complex external stimuli and internal changes. Among these, protein lipidations which refer to lipid attachment to proteins are prominent, which primarily encompassing five types including S-palmitoylation, N-myristoylation, S-prenylation, glycosylphosphatidylinositol (GPI) anchor and cholesterylation. Lipid attachment to proteins plays an essential role in the regulation of protein trafficking, localisation, stability, conformation, interactions and signal transduction by enhancing hydrophobicity. Accumulating evidence from genetic, structural, and biomedical studies has consistently shown that protein lipidation is pivotal in the regulation of broad physiological functions and is inextricably linked to a variety of diseases. Decades of dedicated research have driven the development of a wide range of drugs targeting protein lipidation, and several agents have been developed and tested in preclinical and clinical studies, some of which, such as asciminib and lonafarnib are FDA-approved for therapeutic use, indicating that targeting protein lipidations represents a promising therapeutic strategy. Here, we comprehensively review the known regulatory enzymes and catalytic mechanisms of various protein lipidation types, outline the impact of protein lipidations on physiology and disease, and highlight potential therapeutic targets and clinical research progress, aiming to provide a comprehensive reference for future protein lipidation research.

AMPKα1-mediated ZDHHC8 phosphorylation promotes the palmitoylation of SLC7A11 to facilitate ferroptosis resistance in glioblastoma

The cystine/glutamate antiporter SLC7A11, as the key regulator of ferroptosis, functions to transport cystine for glutathione biosynthesis and antioxidant defense. Accumulating evidence has shown that SLC7A11 is overexpressed in multiple human cancers and promotes tumor growth and progression. However, the exact mechanism underlying this key protein remains unclear. In this study, we confirmed that SLC7A11 is S-palmitoylated in glioblastoma, and this modification is required for SLC7A11 protein stability. Moreover, we revealed that ZDHHC8, a member of the protein palmitoyl transferases (PATs), catalyzes S-palmitoylation of SLC7A11 at Cys327, thereby decreasing the ubiquitination level of SLC7A11. Furthermore, AMPKα1 directly phosphorylates ZDHHC8 at S299, strengthening the interaction between ZDHHC8 and SLC7A11, leading to SLC7A11 S-palmitoylation and deubiquitination. Functional investigations showed that ZDHHC8 knockdown impairs glioblastoma (GBM) cell survival via promoting intracellular ferroptosis events, which could be largely rescued by ectopic expression of SLC7A11. Clinically, ZDHHC8 expression positively correlates with SLC7A11 and AMPKα1 expression in clinical glioma specimens. This study underscores that ZDHHC8-mediated SLC7A11 S-palmitoylation is critical for ferroptosis resistance during GBM tumorigenesis, indicating a novel treatment strategy for GBM.