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Genetic disruption of N-RasG12D palmitoylation perturbs hematopoiesis and prevents myeloid transformation in mice.

ABSTRACT: Oncogenic RAS mutations pose substantial challenges for rational drug discovery. Sequence variations within the hypervariable region of Ras isoforms underlie differential posttranslational modification and subcellular trafficking, potentially resulting in selective vulnerabilities. Specifically, inhibiting the palmitoylation/depalmitoylation cycle is an appealing strategy for treating NRAS mutant cancers, particularly as normal tissues would retain K-Ras4b function for physiologic signaling. The role of endogenous N-RasG12D palmitoylation in signal transduction, hematopoietic differentiation, and myeloid transformation is unknown, and addressing these key questions will inform efforts to develop mechanism-based therapies. To evaluate the palmitoylation/depalmitoylation cycle as a candidate drug target in an in vivo disease-relevant model system, we introduced a C181S mutation into a conditional NrasG12D "knock-in" allele. The C181S second-site amino acid substitution abrogated myeloid transformation by NrasG12D, which was associated with mislocalization of the nonpalmitoylated N-Ras mutant protein, reduced Raf/MEK/ERK signaling, and alterations in hematopoietic stem and progenitor populations. Furthermore, hematologic malignancies arising in NrasG12D/G12D,C181S compound heterozygous mice invariably acquired revertant mutations that restored cysteine 181. Together, these studies validate the palmitoylation cycle as a promising therapeutic target in NRAS mutant cancers.

SUBMITTER: Zambetti NA

PROVIDER: S-EPMC7225687 | biostudies-literature |

REPOSITORIES: biostudies-literature

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Project description:BACKGROUND & AIMS:Intestinal microbiota modulate metabolism and associate closely with epithelial cells in the intestine. In intestinal epithelial cells (IECs), histone deacetylase 3 (HDAC3) integrates microbiota-derived signals to control intestinal homeostasis. We investigated whether HDAC3 in IECs regulates metabolism and the development of obesity in mice. METHODS:Adult C57BL/6 (control) mice and mice with constitutive or inducible IEC-specific disruption of Hdac3 (HDAC3?IEC mice) were placed on a standard chow or high-fat diet (HFD, 60% kcal from fat). We measured body composition, weight, glucose tolerance, and energy expenditure. IECs were isolated from small intestine and gene expression, and lipid levels were analyzed. HDAC3 levels were determined in 43 pediatric patient ileal biopsy samples and compared with body weight. RESULTS:Control mice fed an HFD gained weight, became obese, and had reduced glucose tolerance with increased serum insulin, whereas HFD-fed HDAC3?IEC mice did not develop obesity. Serum levels of triglycerides were reduced in HDAC3?IEC mice, and these mice had less liver fat and smaller adipocytes, compared with HFD-fed control mice. HDAC3?IEC mice had similar food intake and activity as control mice, but higher energy expenditure because of increased catabolism. IECs from HDAC3?IEC mice had altered expression levels of genes that regulate metabolism in response to the microbiota (such as Chka, Mttp, Apoa1, and Pck1) and accumulated triglycerides compared with IECs from control mice. The microbiota-derived short-chain fatty acid butyrate was decreased in obese mice. Butyrate significantly reduced the activity of HDAC3 and increased Pck1 expression in only control IECs. Administration of butyrate to control mice with diet-induced obesity, but not HDAC3?IEC mice, led to significant weight loss. Disruption of HDAC3 in IECs of mice after they became obese led to weight loss and improved metabolic profile. Levels of HDAC3 in intestinal biopsy samples correlated with patient weight. CONCLUSIONS:We found that epithelial HDAC3 promotes development of diet-induced obesity in studies of mice and that butyrate reduces activity of HDAC3 in IECs to prevent diet-induced obesity. This pathway might be manipulated to prevent or reduce obesity-associated disease.

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Genetic disruption of N-RasG12D palmitoylation perturbs hematopoiesis and prevents myeloid transformation in mice.

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