Palmitoylation in Regulating Fyn Kinase Activity Based on FRET Imaging / 医用生物力学

Objective To investigate the molecular mechanism of palmitoylation modification in regulating the activity of non-receptor tyrosine kinase Fyn. Methods The intracellular Fyn activity was detected by applying fluorescence resonance energy transfer (FRET) technology, and the mechanism was investigated by combining with Fyn palmitoylation deficiency and C-terminal Src kinase ( CSK ) plasmid co-expression. ResultsExperimental data showed that single loss of either of ( C3, C6) palmitoylation sites resulted in higher Fyn activity, and C6 seemed more significant. It is known that CSK membrane translocation occurred after activation. FRET assay confirmed that CSK could down-regulate the activity of Fyn in cells, but could not effectively regulate the activity of Fyn(GSS) with the loss of palmitoylation sites. Conclusions The results in this study support the hypothesis on Fyn regulation by spatial localization, namely, non-palmitoylated Fyn (GSS) is less effective in the inhibitory regulation by CSK on cell membrane, thus promoting constitutive high activity expression

Research progress of palmitoylation in non-alcoholic fatty liver disease and related liver diseases / 中国药科大学学报

@#Non-alcoholic fatty liver disease (NAFLD) has become a major public health hazard threatening human health worldwide.Yet, due to its complex pathogenesis, new drug development is difficult, with still insufficient clinical medication.Palmitoylation is a universal posttranslational modification of proteins catalyzed by palmitoyltransferase, affecting their stability, membrane localization and function.Recent studies have shown that palmitoylation is closely associated with NAFLD.This review summarizes the mechanisms of palmitoylation in NAFLD and analyzes the expression levels of the palmitoyltransferase family in liver tissues of NAFLD patients from GEO database, aiming to provide important clues to explore new mechanisms for NAFLD.

ACSL5, a prognostic factor in acute myeloid leukemia, modulates the activity of Wnt/β-catenin signaling by palmitoylation modification / 医学前沿

Acyl-CoA synthetase long chain family member 5 (ACSL5), is a member of the acyl-CoA synthetases (ACSs) family that activates long chain fatty acids by catalyzing the synthesis of fatty acyl-CoAs. The dysregulation of ACSL5 has been reported in some cancers, such as glioma and colon cancers. However, little is known about the role of ACSL5 in acute myeloid leukemia (AML). We found that the expression of ACSL5 was higher in bone marrow cells from AML patients compared with that from healthy donors. ACSL5 level could serve as an independent prognostic predictor of the overall survival of AML patients. In AML cells, the ACSL5 knockdown inhibited cell growth both in vitro and in vivo. Mechanistically, the knockdown of ACSL5 suppressed the activation of the Wnt/β-catenin pathway by suppressing the palmitoylation modification of Wnt3a. Additionally, triacsin c, a pan-ACS family inhibitor, inhibited cell growth and robustly induced cell apoptosis when combined with ABT-199, the FDA approved BCL-2 inhibitor for AML therapy. Our results indicate that ACSL5 is a potential prognosis marker for AML and a promising pharmacological target for the treatment of molecularly stratified AML.

Effect of Porphyromonas gingivalis infection on IFNGR1 palmitoylation in esophageal cancer cells / 南方医科大学学报

OBJECTIVE@#To investigate the effect of Porphyromonas gingivalis (Pg) infection on IFNGR1 palmitoylation and biological behaviors of esophageal squamous cell carcinoma (ESCC) cells and the clinical implications.@*METHODS@#The expression levels of IFNGR1 protein in ESCC cell lines KYSE30 and KYSE70 were detected using Western blotting at 24 and 48 h after Pg infection, and 2-BP was used to detect IFNGR1 palmitoylation in the cells. KYSE70 cells with wild-type IFNGR1 (IFNGR1-WT cells) and with IFNGR1-C122A palmitoylation site mutation induced by site-specific mutagenesis (IFNGR1-C122A cells) were both infected with Pg, and the changes in palmitoylation of IFNGR1-C122A were analyzed using immunofluorescence and Click-iT assays. The changes in proliferation, migration and invasion ability of the infected cells were evaluated using plate cloning assay, scratch assay and Transwell assay, and IFNGR1 co-localization with lysosomal marker LAMP2 was dected using immunofluorescence assay. Immunohistochemistry was used to detect Pg infection and IFNGR1 protein expression in 50 ESCC tissues, and their correlation with the clinicopathological characteristics and survival outcomes of the patients was analyzed.@*RESULTS@#Pg infection down-regulated the protein expression of IFNGR1 in ESCC and promoted IFNGR1 palmitoylation at site 122. In IFNGR1-WT cells, Pg infection significantly enhanced cell proliferation, migration and invasion (P < 0.05). Similarly, Pg also significantly promoted proliferation, migration and invasion of IFNGR1-C122A cells, but to a lesser extent as compared with the wild-type cells (P < 0.05). Immunofluorescence assay showed that Pg and ZDHHC3 promoted IFNGR1 degradation within the lysosome. Immunohistochemical studies of the ESCC tissue samples showed a negative correlation between IFNGR1 and Pg expression, and a reduced IFNGR1 expression was correlated with a poorer survival outcome of the patient.@*CONCLUSION@#Pg infection enhances IFNGR1 palmitoylation to promote progression of ESCC, and elimination of Pg and inhibiting IFNGR1 palmitoylation may effectively control ESCC progression.

ZDHHC12-mediated claudin-3 -palmitoylation determines ovarian cancer progression

The membrane protein claudin-3 (CLDN3) is critical for the formation and maintenance of tight junction and its high expression has been implicated in dictating malignant progression in various cancers. However, the post-translational modification of CLDN3 and its biological function remains poorly understood. Here, we report that CLDN3 is positively correlated with ovarian cancer progression both and Of interest, CLDN3 undergoes -palmitoylation on three juxtamembrane cysteine residues, which contribute to the accurate plasma membrane localization and protein stability of CLDN3 Moreover, the deprivation of -palmitoylation in CLDN3 significantly abolishes its tumorigenic promotion effect in ovarian cancer cells. By utilizing the co-immunoprecipitation assay, we further identify ZDHHC12 as a CLDN3-targating palmitoyltransferase from 23 ZDHHC family proteins. Furthermore, the knockdown of ZDHHC12 also significantly inhibits CLDN3 accurate membrane localization, protein stability and ovarian cancer cells tumorigenesis Thus, our work reveals -palmitoylation as a novel regulatory mechanism that modulates CLDN3 function, which implies that targeting ZDHHC12-mediated CLDN3 -palmitoylation might be a potential strategy for ovarian cancer therapy.

Subcellular localisation of FLAG tagged enzymes of the dynamic protein S-palmitoylation cycle of Trypanosoma cruzi epimastigotes

Dynamic S-palmitoylation of proteins is the addition of palmitic acid by zDHHC palmitoyl transferases (PATs) and depalmitoylation by palmitoyl protein thioesterases (PPTs). A putative PAT (TcPAT1) has been previously identified in Trypanosoma cruzi, the etiological agent of Chagas disease. Here we analyse other 14 putative TcPATs and 2 PPTs in the parasite genome. T. cruzi cell lines expressing TcPATs and TcPPTs plus a FLAG tag at the C terminus were produced for most enzymes, with positive detection by indirect immunofluorescence. Overexpressed TcPATs were mostly found as single spots at the parasite anterior end, while the TcPPTs were dispersed throughout the parasite body.

Multifactorial Regulation of G Protein-Coupled Receptor Endocytosis

Endocytosis is a process by which cells absorb extracellular materials via the inward budding of vesicles formed from the plasma membrane. Receptor-mediated endocytosis is a highly selective process where receptors with specific binding sites for extracellular molecules internalize via vesicles. G protein-coupled receptors (GPCRs) are the largest single family of plasma-membrane receptors with more than 1000 family members. But the molecular mechanisms involved in the regulation of GPCRs are believed to be highly conserved. For example, receptor phosphorylation in collaboration with β-arrestins plays major roles in desensitization and endocytosis of most GPCRs. Nevertheless, a number of subsequent studies showed that GPCR regulation, such as that by endocytosis, occurs through various pathways with a multitude of cellular components and processes. This review focused on i) functional interactions between homologous and heterologous pathways, ii) methodologies applied for determining receptor endocytosis, iii) experimental tools to determine specific endocytic routes, iv) roles of small guanosine triphosphate-binding proteins in GPCR endocytosis, and v) role of post-translational modification of the receptors in endocytosis.

Retainment of membrane binding capacity of non-palmitoylated Gs alpha mutants expressed in COS-1 cells

Heterotrimeric guanine nucleotide binding regulatory proteins (G proteins) transduce extracellular signals into intracellular signals by coupling receptors and effectors. Because most of the G protein-coupled receptors are integral proteins, the G proteins need to have a membrane binding capacity to receive signals from the receptors. The alpha subunit of G protein binds tightly to the cytoplasmic face of the plasma membrane without any membrane spanning domain. Fatty acylation of G alpha with myristic acid or palmitic acid, in addition to the beta gamma subunits, plays an important role in anchoring the G alpha subunit. The reversible and dynamic palmitoylation of the alpha subunit of stimulatory G protein (Gs alpha) has been suggested as essential for its membrane attachment. However, in our previous experiments, Gs alpha deleted in the amino terminus containing palmitoylation site, retained its binding capacity when expressed in COS cells. Thus, to evaluate the role of palmitoylation in Gs alpha membrane binding, we constructed and expressed non-palmitoylated mutants of Gs alpha and analyzed their subcellular distributions in COS-1 cells. We found that non-palmitoylated mutants of Gs alpha, C3S- and G2A/C3S Gs alpha, retained their membrane binding capacities in COS-1 cells, demonstrating that palmitoylation is not essential for membrane binding of Gs alpha in COS-1 cells. We also found that the palmitoylation did not change significantly the distribution of Gs alpha in Triton X-114 partition. These results suggest that the palmitoylation of Gs alpha may produce different effects on membrane binding depending on cell types.