ABSTRACT
A commonality between type 1 and type 2 diabetes is the decline in functional ß-cell mass. The transcription factor Nkx6.1 regulates ß-cell development and is integral for proper ß-cell function. We have previously demonstrated that Nkx6.1 depends on c-Fos mediated upregulation and the nuclear hormone receptors Nr4a1 and Nr4a3 to increase ß-cell insulin secretion, survival, and replication. Here, we demonstrate that Nkx6.1 overexpression results in upregulation of the bZip transcription factor CEBPA and that CEBPA expression is independent of c-Fos regulation. In turn, CEBPA overexpression is sufficient to enhance INS-1 832/13 ß-cell and primary rat islet proliferation. CEBPA overexpression also increases the survival of ß-cells treated with thapsigargin. We demonstrate that increased survival in response to ER stress corresponds with changes in expression of various genes involved in the unfolded protein response, including decreased Ire1a expression. These data show that CEBPA is sufficient to enhance functional ß-cell mass by increasing ß-cell proliferation and modulating the unfolded protein response.
ABSTRACT
Metabolic networks are interconnected and influence diverse cellular processes. The protein-metabolite interactions that mediate these networks are frequently low affinity and challenging to systematically discover. We developed mass spectrometry integrated with equilibrium dialysis for the discovery of allostery systematically (MIDAS) to identify such interactions. Analysis of 33 enzymes from human carbohydrate metabolism identified 830 protein-metabolite interactions, including known regulators, substrates, and products as well as previously unreported interactions. We functionally validated a subset of interactions, including the isoform-specific inhibition of lactate dehydrogenase by long-chain acyl-coenzyme A. Cell treatment with fatty acids caused a loss of pyruvate-lactate interconversion dependent on lactate dehydrogenase isoform expression. These protein-metabolite interactions may contribute to the dynamic, tissue-specific metabolic flexibility that enables growth and survival in an ever-changing nutrient environment.
Subject(s)
Carbohydrate Metabolism , L-Lactate Dehydrogenase , Metabolome , Humans , Fatty Acids/metabolism , L-Lactate Dehydrogenase/metabolism , Organ Specificity , Mass Spectrometry/methods , Allosteric RegulationABSTRACT
The homeobox transcription factor Nkx6.1 is sufficient to increase functional ß-cell mass, where functional ß-cell mass refers to the combination of ß-cell proliferation, glucose-stimulated insulin secretion (GSIS) and ß-cell survival. Here, we demonstrate that the histone deacetylase 1 (HDAC1), which is an early target of Nkx6.1, is sufficient to increase functional ß-cell mass. We show that HDAC activity is necessary for Nkx6.1-mediated proliferation, and that HDAC1 is sufficient to increase ß-cell proliferation in primary rat islets and the INS-1 832/13 ß-cell line. The increase in HDAC1-mediated proliferation occurs while maintaining GSIS and increasing ß-cell survival in response to apoptotic stimuli. We demonstrate that HDAC1 overexpression results in decreased expression of the cell cycle inhibitor Cdkn1b/p27 which is essential for inhibiting the G1 to S phase transition of the cell cycle. This corresponds with increased expression of key cell cycle activators, such as Cyclin A2, Cyclin B1 and E2F1, which are activated by activation of the Cdk4/Cdk6/Cyclin D holoenzymes due to down-regulation of Cdkn1b/p27. Finally, we demonstrate that overexpression of Cdkn1b/p27 inhibits HDAC1-mediated ß-cell proliferation. Our data suggest that HDAC1 is critical for the Nkx6.1-mediated pathway that enhances functional ß-cell mass.
Subject(s)
Cell Proliferation/physiology , Cyclin-Dependent Kinase Inhibitor p27/metabolism , Down-Regulation/physiology , Gene Expression Regulation, Enzymologic , Histone Deacetylase 1/biosynthesis , Insulin-Secreting Cells/metabolism , Animals , Cells, Cultured , Cyclin-Dependent Kinase Inhibitor p27/antagonists & inhibitors , Cyclin-Dependent Kinase Inhibitor p27/genetics , Histone Deacetylase 1/genetics , Humans , Male , Rats , Rats, WistarABSTRACT
Malignant lipomatous tumors of the vulva are uncommon. We present 2 cases of liposarcoma arising in the vulva: a myxoid liposarcoma harboring DDIT3 and FUS rearrangements and a well differentiated liposarcoma/atypical lipomatous tumor harboring MDM2 amplification detected by fluorescence in situ hybridization. Both cases are the first liposarcomas of this site to be confirmed by molecular cytogenetic analysis. We also review the literature's cases of liposarcoma to further examine the clinicopathologic features of these tumors.
