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Abstract Objective The metabolic role of d -serine, a non-proteinogenic NMDA receptor co-agonist, is poorly understood. Conversely, inhibition of pancreatic NMDA receptors as well as loss of the d -serine producing enzyme serine racemase have been shown to modulate insulin secretion. Thus, we aim to study the impact of chronic and acute d -serine supplementation on insulin secretion and other parameters of glucose homeostasis. Methods We apply MALDI FT-ICR mass spectrometry imaging, NMR based metabolomics, 16s rRNA gene sequencing of gut microbiota in combination with a detailed physiological characterization to unravel the metabolic action of d -serine in mice acutely and chronically treated with 1% d -serine in drinking water in combination with either chow or high fat diet feeding. Moreover, we identify SNPs in SRR, the enzyme converting L-to d -serine and two subunits of the NMDA receptor to associate with insulin secretion in humans, based on the analysis of 2760 non-diabetic Caucasian individuals. Results We show that chronic elevation of d -serine results in reduced high fat diet intake. In addition, d -serine leads to diet-independent hyperglycemia due to blunted insulin secretion from pancreatic beta cells. Inhibition of alpha 2-adrenergic receptors rapidly restores glycemia and glucose tolerance in d -serine supplemented mice. Moreover, we show that single nucleotide polymorphisms (SNPs) in SRR as well as in individual NMDAR subunits are associated with insulin secretion in humans. Conclusion Thus, we identify a novel role of d -serine in regulating systemic glucose metabolism through modulating insulin secretion. Highlights • d -serine suppresses HFD induced weight gain. • d -serine supplementation impairs insulin secretion. • d -serine effects on insulin secretion can be reverted by a2 adrenergic antagonists. [ABSTRACT FROM AUTHOR]

Molecular mechanisms underlying adaptive targeted therapy resistance in pancreatic ductal adenocarcinoma (PDAC) are poorly understood. Here, we identify SETD5 as a major driver of PDAC resistance to MEK1/2 inhibition (MEKi). SETD5 is induced by MEKi resistance and its deletion restores refractory PDAC vulnerability to MEKi therapy in mouse models and patient-derived xenografts. SETD5 lacks histone methyltransferase activity but scaffolds a co-repressor complex, including HDAC3 and G9a. Gene silencing by the SETD5 complex regulates known drug resistance pathways to reprogram cellular responses to MEKi. Pharmacological co-targeting of MEK1/2, HDAC3, and G9a sustains PDAC tumor growth inhibition in vivo. Our work uncovers SETD5 as a key mediator of acquired MEKi therapy resistance in PDAC and suggests a context for advancing MEKi use in the clinic. • SETD5 is an epigenetic driver of pancreatic cancer resistance to MEK1/2 inhibition • SETD5 has no intrinsic methylation activity on histones, including at H3 lysine 36 • A SETD5 co-repressor complex regulates a network of drug resistance pathways • Co-targeting of MEK1/2 and the SETD5 complex results in sustained tumor inhibition In pancreatic ductal adenocarcinoma (PDAC), a major roadblock in therapies targeting the KRAS-MAPK pathway, such as MEK1/2 inhibition (MEKi), is the rapid emergence of resistance. Wang et al. identify a clinically actionable epigenetic pathway mediated by SETD5 to drive PDAC resistance to MEKi. [ABSTRACT FROM AUTHOR]

Protein synthesis is a fundamental step in gene expression, with modulation of mRNA translation at the elongation step emerging as an important regulatory node in shaping cellular proteomes. In this context, five distinct lysine methylation events on eukaryotic elongation factor 1A (eEF1A), a fundamental nonribosomal elongation factor, are proposed to influence mRNA translation elongation dynamics. However, a lack of affinity tools has hindered progress in fully understanding how eEF1A lysine methylation impacts protein synthesis. Here we develop and characterize a suite of selective antibodies to investigate eEF1A methylation and provide evidence that methylation levels decline in aged tissue. Determination of the methyl state and stoichiometry on eEF1A in various cell lines by mass spectrometry shows modest cell-tocell variability. We also find by Western blot analysis that knockdown of individual eEF1A-specific lysine methyltransferases leads to depletion of the cognate lysine methylation event and indicates active crosstalk between different sites. Further, we find that the antibodies are specific in immunohistochemistry applications. Finally, application of the antibody toolkit suggests that several eEF1A methylation events decrease in aged muscle tissue. Together, our study provides a roadmap for leveraging methyl state and sequenceselective antibody reagents to accelerate discovery of eEF1A methylation-related functions and suggests a role for eEF1A methylation, via protein synthesis regulation, in aging biology. [ABSTRACT FROM AUTHOR]