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Biology subjects

Ramms, D. J.

Publications and source records attributed to Ramms, D. J..

3 recordsLinked to original sources

Pancreatic Gαs ablation disrupts tissue architecture and YAP signaling and unveils a compensatory regenerative response

Diabetes mellitus is characterized by chronic hyperglycemia and loss of pancreatic {beta}-cell function and mass. Current therapies focus on {beta}-cell protection and regeneration, led by GLP-1 receptor agonists. The G protein -subunit (Gs) acts as a key signaling node downstream of numerous GPCRs, integrating diverse signals that impact {beta}-cell mass and function. Elucidating the integrative role of pancreatic Gs signaling is thus crucial for understanding {beta}-cell biology. Our map of the pancreatic Gs-coupled GPCR landscape reveals sophisticated, cell-type-specific networks, positioning Gs as a central hub for intra-pancreatic communication. Previous studies in mice with {beta}-cell-specific or whole-pancreatic Gs deletion demonstrated reduced {beta}-cell mass, impaired insulin secretion, and glucose intolerance. The stronger phenotype in the whole-pancreas model--marked by -cell expansion and abnormal distribution--points to a crucial role for Gs in differential control of postnatal - and {beta}-cell proliferation. Here, we analyze the organ-wide consequences of Gs deletion using pancreas-specific Gs knockout mice (PGsKO). Consistent with prior findings, PGsKO mice exhibit reduced weight gain from four weeks and severe diabetes due to decreased {beta}-cell mass and concomitant -cell expansion. Furthermore, Gs loss induces profound architectural and functional defects in the exocrine pancreas, linked to YAP reactivation in acinar cells. Importantly, we observed attempted {beta}-cell regeneration in PGsKO mice. Although insufficient to reverse diabetes, our results delineate the full pancreatic phenotype that may facilitate these regenerative efforts and suggest that strategically biasing GPCR signaling network away from Gs could be a viable strategy to promote {beta}-cell regeneration from other pancreatic cell types. ARTICLE HIGHLIGHTSO_LIGs is a central signaling hub that integrates diverse GPCR inputs across pancreatic cell types, yet its organ-wide role remained poorly defined. C_LIO_LIWe addressed how pancreas-wide Gs deletion disrupts both endocrine and exocrine compartments, and whether regenerative programs are engaged. C_LIO_LIGs loss caused severe diabetes through {beta}-cell loss and -cell expansion, induced profound exocrine defects with YAP reactivation, and triggered attempted {beta}-cell regeneration from ducts and potentially other cell types. C_LIO_LIOur findings suggest that strategically biasing GPCR signaling away from Gs could promote regeneration from non-{beta}-cell sources, offering new therapeutic avenues for diabetes. C_LI

cell biology↗

The COX2-PGE2-PKA Axis Suppresses Antiviral Immunity by Inhibiting mtDNA-Dependent STING Activation.

The innate immune cGAS-STING pathway is activated by cytosolic double-stranded DNA (dsDNA) to induce type I interferon (IFN) response, which is essential for mounting the antiviral response. However, STING activation during viral infection is often insufficient to achieve complete viral clearance, suggesting the existence of additional mechanisms that evade its activity. Here, we identified COX2/PGE2 as a negative regulator of STING activation, particularly in response to arising cytosolic mitochondrial DNA (mtDNA) generated during HSV-1 infection. Mechanistically, PGE2, through the EP4-cAMP-PKA axis, induces mitophagy to remove defective mitochondria and hence prevent the accumulation of immunostimulatory cytosolic mtDNA, thereby dampening STING-mediated type I IFN and antiviral response. Furthermore, we identified STOML2 as a downstream target of PKA that connects mitochondrial quality control with the regulation of innate immune signaling. Together, our findings establish the COX2/PGE2/PKA axis as a negative regulator of mtDNA-STING signaling that may be targeted to potentiate STING-mediated type I IFN and innate immunity. O_FIG O_LINKSMALLFIG WIDTH=166 HEIGHT=200 SRC="FIGDIR/small/716411v1_ufig1.gif" ALT="Figure 1"> View larger version (35K): org.highwire.dtl.DTLVardef@1c39d56org.highwire.dtl.DTLVardef@18e7c0eorg.highwire.dtl.DTLVardef@172b353org.highwire.dtl.DTLVardef@15b215a_HPS_FORMAT_FIGEXP M_FIG O_FLOATNOGraphical abstractC_FLOATNO C_FIG

cell biology↗

A reversible SRC-relayed COX2-inflammatory program drives therapeutic resistance in BRAF(V600E) colorectal tumors

BRAFV600E mutation confers a poor prognosis in metastatic colorectal cancer (CRC) despite combinatorial targeted therapies based on the latest understanding of signaling circuitry. To identify parallel resistance mechanisms induced by BRAF/MEK/EGFR co-targeting, we used a high throughput kinase activity mapping platform. We found that SRC kinases are systematically activated in BRAFV600E CRC following targeted inhibition of BRAF {+/-} EGFR, and that coordinated targeting of SRC with BRAF {+/-} EGFR increases efficacy in vitro and in vivo. SRC drives resistance to BRAF {+/-} anti-EGFR therapy independently of ERK signaling by inducing transcriptional reprogramming via beta-catenin (CTNNB1). The EGFR-independent compensatory activation of SRC kinases is mediated by an autocrine prostaglandin E2-loop that can be blocked with cyclooxygenase-2 (COX2) inhibitors. Co-targeting of COX2 with BRAF+EGFR promotes durable suppression of tumor growth in patient-derived tumor xenograft (PDX) models. COX2 inhibition represents a novel drug-repurposing strategy to overcome therapeutic resistance in BRAFV600E CRC.

cancer biology↗