Mussbacher, M. | Search bioRxiv

bioRxiv2025

The cytosolic PRMT5-CDK4 complex impairs cell cycle kinase signaling

Both, protein arginine methyltransferases (PRMTs) and protein kinases are critical regulators of cellular processes and frequently dysregulated in malignancy. To systematically study the crosstalk of the two regulatory enzyme classes, we used parallel yeast two-hybrid matrix screening and defined 45 interactions connecting 4 PRMTs and 20 human kinases. The PRMT-kinase network revealed a strong association between PRMTs and cell cycle/mitogen-activated kinases. Notably, the PRMT5-CDK4 emerged as the most prominent functional cell cycle link through integrative data analyses of different high-throughput datasets. Mechanistic cell biological studies confirmed that the PRMT5-CDK4 complex localizes exclusively in the cytosol, where its formation was enhanced during a G1/S cell cycle block. This PRMT5 interaction modulated the CDK4-CCND3 and CDK4-CDKN2A interaction dynamics, irrespective of PRMT5s methyltransferase activity. Phospho-proteomic profiling demonstrated that PRMT5 overexpression functionally phenocopies the signaling effects of pharmacological CDK4 inhibition with Palbociclib. The findings establish a non-enzymatic regulatory role for PRMT5, proposing it functions as an inhibitory modulator of CDK4-driven oncogenic signaling.

systems biology↗

bioRxiv2023

Neutrophil-specific STAT4 deficiency reduces atherogenesis and improves plaque stability via reduced neutrophil activation and recruitment to aortas.

Background and AimsNeutrophils drive atheroprogression and directly contribute to plaque instability. We recently identified signal transducer and activator of transcription 4 (STAT4) as a critical component for bacterial host defense in neutrophils. The STAT4-dependent functions of neutrophils in atherogenesis are unknown. Therefore, we investigated a contributory role of STAT4 in neutrophils during advanced atherosclerosis. MethodsWe generated myeloid-specific Stat4{Delta}LysMLdlr-/-, neutrophil-specific Stat4{Delta}S100A8 Ldlr-/-, and control Stat4fl/flLdlr-/- mice. All groups were fed a high-fat/cholesterol diet (HFD-C) for 28 weeks to establish advanced atherosclerosis. Aortic root plaque burden and stability were assessed histologically by Movat Pentachrome staining. Nanostring gene expression analysis was performed on isolated blood neutrophils. Flow cytometry was utilized to analyze hematopoiesis and blood neutrophil activation. In vivo homing of neutrophils to atherosclerotic plaques was performed by adoptively transferring prelabeled Stat4{Delta}LysMLdlr-/- and Stat4fl/flLdlr-/- bone marrow cells into aged atherosclerotic Apoe-/- mice and detected by flow cytometry. ResultsSTAT4 deficiency in both myeloid-specific and neutrophil-specific mice provided similar reductions in aortic root plaque burden and improvements in plaque stability via reduction in necrotic core size, improved fibrous cap area, and increased vascular smooth muscle cell content within the fibrous cap. Myeloid-specific STAT4 deficiency resulted in decreased circulating neutrophils via reduced production of granulocyte-monocyte progenitors in the bone marrow. Neutrophil activation was dampened in Stat4{Delta}LysMLdlr-/- mice via reduced mitochondrial superoxide production, attenuated surface expression of degranulation marker CD63, and reduced frequency of neutrophil-platelet aggregates. Myeloid-specific STAT4 deficiency diminished expression of chemokine receptors CCR1 and CCR2 and impaired in vivo neutrophil trafficking to atherosclerotic aorta. ConclusionsOur work indicates a pro-atherogenic role for STAT4-dependent neutrophil activation and how it contributes to multiple factors of plaque instability during advanced atherosclerosis in mice.

immunology↗