Tris DBA palladium is highly effective against growth and metastasis of pancreatic cancer in an orthotopic model

Pancreatic carcinoma ranks among the most lethal of human cancers. Besides late detection, other factors contribute to its lethality, including a high degree of chemoresistance, invasion, and distant metastases. Currently, the mainstay of therapy involves resection of local disease in a minority of patients (Whipple procedure) and systemic gemcitabine. While systemic chemotherapy has some benefit, even with optimal treatment, the five year survival after diagnosis is dismal. Thus, treatment of pancreatic carcinoma remains a tremendous unmet need.

The organometallic compound tris DBA palladium is a potent inhibitor of N-myristoyltransferase 1 (NMT1), an enzyme that catalyzes the transfer of myristate to protein substrates. This compound is highly effective in vivo against murine models of melanoma with both mutant and wild type b-RAF genotypes. Based upon the signaling similarities between melanoma and pancreatic carcinoma, we evaluated the efficacy of tris DBA palladium in vitro and in vivo against pancreatic carcinoma. We found that tris DBA palladium decreased proliferation and colony formation of pancreatic cancer cells in vitro. In an orthotopic mouse model, tris DBA palladium was highly active in inhibiting growth, ascites production, and distant metastases in vivo. Furthermore, tris DBA palladium impaired chemotaxis and inhibited cilia formation in Pan02 cells in a NMT1-dependent manner. We propose that NMT1 is a novel regulator of cilia formation and tris DBA palladium a novel inhibitor of cilia formation and metastasis in pancreatic cancer. Thus, further evaluation of tris DBA palladium for the treatment of pancreatic cancer is warranted.

N-myristoyltransferase-1 deficiency blocks myristoylation of LAMTOR1 and inhibits bladder cancer progression

N-myristoyltransferase-1 (NMT1) catalyzes protein posttranslational myristoylation and functions as an oncogene in various cancers, although its roles in bladder cancer remain elusive. Here, we demonstrated that NMT1 was obviously upregulated in bladder cancer and correlated with overall survival and poor prognosis. Elevation of NMT1 promotes cancer progression and inhibits autophagy in vitro and in vivo. Furthermore, we confirm that LAMTOR1 was myristoylated by NMT1 at Gly 2, resulting in increased LAMTOR1 protein stability and lysosomal localization. Importantly, B13, an inhibitor of NMT1 enzymatic activity, exerted its anti-tumor effects against bladder cancer cells in vitro and in vivo. Taken together, these findings uncover a molecular mechanism of NMT1 in modulating bladder cancer progression and indicate that targeting NMT1 may represent a novel clinical intervention in bladder cancer.

N-Terminal Acetyltransferase Naa40p Whereabouts Put into N-Terminal Proteoform Perspective

The evolutionary conserved N-alpha acetyltransferase Naa40p is among the most selective N-terminal acetyltransferases (NATs) identified to date. Here we identified a conserved N-terminally truncated Naa40p proteoform named Naa40p25 or short Naa40p (Naa40^S). Intriguingly, although upon ectopic expression in yeast, both Naa40p proteoforms were capable of restoring N-terminal acetylation of the characterized yeast histone H2A Naa40p substrate, the Naa40p histone H4 substrate remained N-terminally free in human haploid cells specifically deleted for canonical Naa40p27 or 237 amino acid long Naa40p (Naa40^L), but expressing Naa40^S. Interestingly, human Naa40^L and Naa40^S displayed differential expression and subcellular localization patterns by exhibiting a principal nuclear and cytoplasmic localization, respectively. Furthermore, Naa40^L was shown to be N-terminally myristoylated and to interact with N-myristoyltransferase 1 (NMT1), implicating NMT1 in steering Naa40^L nuclear import. Differential interactomics data obtained by biotin-dependent proximity labeling (BioID) further hints to context-dependent roles of Naa40p proteoforms. More specifically, with Naa40^S representing the main co-translationally acting actor, the interactome of Naa40^L was enriched for nucleolar proteins implicated in ribosome biogenesis and the assembly of ribonucleoprotein particles, overall indicating a proteoform-specific segregation of previously reported Naa40p activities. Finally, the yeast histone variant H2A.Z and the transcriptionally regulatory protein Lge1 were identified as novel Naa40p substrates, expanding the restricted substrate repertoire of Naa40p with two additional members and further confirming Lge1 as being the first redundant yNatA and yNatD substrate identified to date.

Long noncoding RNA ANCR promotes migration, invasion, EMT progress and stemness of nasopharyngeal carcinoma cells via the miR-4731-5p/NMT1 axis

BACKGROUND

In our previous study, we revealed that Antidifferentiation noncoding RNA (ANCR) promoted proliferation and radiation resistance of nasopharyngeal carcinoma (NPC) cells. However, the molecular mechanism and function of ANCR are not fully studied. The current study aimed to further investigate the role and underlying molecular mechanism of ANCR in NPC.

METHODS

RT-qPCR and western blot analyses were used to detect the levels of RNAs and proteins in NPC cells. Wound healing and Transwell assays were used to examine the migration and invasion of NPC cells. The relationship among ANCR, miR-4731-5p and N-myristoyltransferase 1 (NMT1) was investigated by RIP and luciferase reporter assays. The NPC cell stemness was accessed by the sphere formation assay.

RESULTS

ANCR was significantly highly expressed in NPC cell lines. Silenced ANCR suppressed cell migration, invasion epithelial-mesenchymal transition (EMT) process and cell stemness in NPC. Furthermore, ANCR sponged miR-4731-5p to upregulate the NMT1 expression. Rescue assays indicated that NMT1 neutralized the antioncogenic effect induced by silenced ANCR on NPC cells.

CONCLUSIONS

Long noncoding RNA ANCR suppresses malignant behaviors of nasopharyngeal carcinoma cells by regulating miR-4731-5p/NMT1 axis.

TNF-α-induced Inhibition of Protein Myristoylation Via Binding Between NMT1 and Sorbs2 in Osteoblasts

BACKGROUND/AIM

Bone resolution due to tumor invasion often occurs on the surface of the jaw and is important for clinical prognosis. Although cytokines, such as TNF-α are known to impair osteoblasts, the underlying mechanism remains unclear. Protein myristoylation, a post-translational modification, plays an important role in the development of immune responses and cancerization of cells. A clear understanding of the mechanisms underlying this involvement will provide insights into molecular-targeted therapies. N-myristoyltransferase1 (NMT1), a specific enzyme involved in myristoylation, is expressed in cancer cells and in other normal cells, suggesting that changes in myristoylation may result from the regulation of NMT1 in cancer cells.

MATERIALS AND METHODS

Using newly emerging state-of-the-art techniques such as the Click-it assay, RNA interference, mass spectrometry, immunoprecipitation, immunocytochemistry, and western blotting, the expression of myristoylated proteins and the role of TNF-α stimulation on NMT1 and Sorbs2 binding were evaluated in a murine osteoblastic cell line (MC3T3-E1).

RESULTS

The expression of myristoylated proteins was detected; however, TNF-α stimulation resulted in their inhibition in MC3T3-E1 cells. The expression of NMT1 also increased. Immunoprecipitation and mass spectrometry identified Sorbs2 as a novel binding protein of NMT1, which upon TNF-α stimulation, inhibited myristoylation.

CONCLUSION

The binding between NMT1 and Sorbs2 can regulate myristoylation, and NMT1 can be considered as a potential target molecule for tumor invasion.

The V2 Protein from the Geminivirus Tomato Yellow Leaf Curl Virus Largely Associates to the Endoplasmic Reticulum and Promotes the Accumulation of the Viral C4 Protein in a Silencing Suppression-Independent Manner

Viruses are strict intracellular parasites that rely on the proteins encoded in their genomes for the effective manipulation of the infected cell that ultimately enables a successful infection. Viral proteins have to be produced during the cell invasion and takeover in sufficient amounts and in a timely manner. Silencing suppressor proteins evolved by plant viruses can boost the production of viral proteins; although, additional mechanisms for the regulation of viral protein production likely exist. The strongest silencing suppressor encoded by the geminivirus tomato yellow leaf curl virus (TYLCV) is V2: V2 suppresses both post-transcriptional and transcriptional gene silencing (PTGS and TGS), activities that are associated with its localization in punctate cytoplasmic structures and in the nucleus, respectively. However, V2 has been previously described to largely localize in the endoplasmic reticulum (ER), although the biological relevance of this distribution remains mysterious. Here, we confirm the association of V2 to the ER in Nicotiana benthamiana and assess the silencing suppression activity-independent impact of V2 on protein accumulation. Our results indicate that V2 has no obvious influence on the localization of ER-synthesized receptor-like kinases (RLKs) or ER quality control (ERQC)/ER-associated degradation (ERAD), but dramatically enhances the accumulation of the viral C4 protein, which is co-translationally myristoylated, possibly in proximity to the ER. By using the previously described V2_C84S/86S mutant, in which the silencing suppression activity is abolished, we uncouple RNA silencing from the observed effect. Therefore, this work uncovers a novel function of V2, independent of its capacity to suppress silencing, in the promotion of the accumulation of another crucial viral protein.

VP0 Myristoylation Is Essential for Senecavirus A Replication

Many picornaviruses require the myristoylation of capsid proteins for viral replication. Myristoylation is a site-specific lipidation to the N-terminal G residue of viral proteins, which is catalyzed by the ubiquitous eukaryotic enzyme N-myristoyltransferase (NMT) by allocating the myristoyl group to the N-terminal G residue. IMP-1088 and DDD85646 are two inhibitors that can deprive NMT biological functions. Whether Senecavirus A (SVA) uses NMT to modify VP0 and regulate viral replication remains unclear. Here, we found that NMT inhibitors could inhibit SVA replication. NMT1 knock-out in BHK-21 cells significantly suppressed viral replication. In contrast, the overexpression of NMT1 in BHK-21 cells benefited viral replication. These results indicated that VP0 is a potential NMT1 substrate. Moreover, we found that the myristoylation of SVA VP0 was correlated to the subcellular distribution of this protein in the cytoplasm. Further, we evaluated which residues at the N-terminus of VP0 are essential for viral replication. The substitution of N-terminal G residue, the myristoylation site of VP0, produced a nonviable virus. The T residue at the fifth position of the substrates facilitates the binding of the substrates to NMT. And our results showed that the T residue at the fifth position of VP0 played a positive role in SVA replication. Taken together, we demonstrated that SVA VP0 myristoylation plays an essential role in SVA replication.

Inhibition of N-myristoyltransferase activity promotes androgen receptor degradation in prostate cancer

BACKGROUND

Even though prostate cancer (PCa) patients initially respond to androgen deprivation therapy, some will eventually develop castration resistant prostate cancer (CRPC). Androgen receptor (AR) mediated cell signaling is a major driver in the progression of CRPC while only a fraction of PCa becomes AR negative. This study aimed to understand the regulation of AR levels by N-myristoyltransferase in PCa cells.

METHODS

Two enantiomers, (1S,2S)- d-NMAPPD and (1R,2R)- d-NMAPPD (LCL4), were characterized by various methods (1 H and 13 C NMR, UHPLC, high-resolution mass spectra, circular dichroism) and evaluated for the ability to bind to N-myristoyltransferase 1 (NMT1) using computational docking analysis. structure-activity relationship analysis of these compounds led to the synthesis of (1R,2R)-LCL204 and evaluation as a potential NMT1 inhibitor utilizing the purified full length NMT1 enzyme. The NMT inhibitory activity wase determined by Click chemistry and immunoblotting. Regulation of NMT1 on tumor growth was evaluated in a xenograft tumor model.

RESULTS

(1R,2R)- d-NMAPPD, but not its enantiomer (1S,2S)- d-NMAPPD, inhibited NMT1 activity and reduced AR protein levels. (1R,2R)-LCL204, a derivative of (1R,2R)- d-NMAPPD, inhibited global protein myristoylation. It also suppressed protein levels, nuclear translocation, and transcriptional activity of AR full-length or variants in PCa cells. This was due to enhanced ubiquitin and proteasome-mediated degradation of AR. Knockdown of NMT1 levels inhibited tumor growth and proliferation of cancer cells.

CONCLUSION

Inhibitory efficacy on N-myristoyltransferase activity by d-NMAPPD is stereospecific. (1R,2R)-LCL204 reduced global N-myristoylation and androgen receptor protein levels at low micromolar concentrations in prostate cancer cells. pharmacological inhibition of NMT1 enhances ubiquitin-mediated proteasome degradation of AR. This study illustrates a novel function of N-myristoyltransferase and provides a potential strategy for treatment of CRPC.

NMT1 Enhances the Stemness of NSCLC Cells by Activating the PI3K/AKT Pathway

INTRODUCTION

Abundant studies have disclosed that proteins can function as pivotal tumor promoters or suppressors in cancers' progression. This work was planned to investigate the regulatory function of N-myristoyltransferase-1 (NMT1) on non-small cell lung cancer (NSCLC) and the underlying molecular mechanisms.

METHODS

The self-renewal abilities were assessed through a spheroid-formation assay. The tumorigenic abilities were examined through nude mice in vivo assay. The proteins' expression was measured through Western blot. The NMT1 protein expression in tumor tissues was measured through an IHC assay. The cell migration and invasion was confirmed through a transwell assay. The IC50 was verified through a CCK-8 assay. The NMT1 mRNA expression in NSCLC tissues was detected through RT-qPCR.

RESULTS

It was demonstrated that NMT1 exhibited higher expression in spheroid cells. Additionally, NMT1 facilitated the stemness in NSCLC. It was also found that NMT1 accelerated NSCLC tumor metastasis and the resistance to cisplatin. Moreover, NMT1 activated the PI3K/AKT pathway to facilitate stemness in NSCLC. NMT1 was also higher in tumor tissues of NSCLC patients and resulted in a poor survival rate.

CONCLUSION

NMT1 enhanced the stemness of NSCLC cells by activating the PI3K/AKT pathway. This discovery suggested that NMT1 may be a valid therapeutic biomarker for NSCLC.