Biology subjects

Bracher, F.

Publications and source records attributed to Bracher, F..

4 recordsLinked to original sources

bioRxiv2024

Sirtuin2 blockade inhibits replication of Human Immunodeficiency Virus-1 and 1 Mycobacterium tuberculosis in macrophages and humanized mice

Coinfections with Mycobacterium tuberculosis (Mtb) and HIV-1 present a critical health challenge and require treatment for survival. We found that human M1 macrophages inhibit Mtb growth, while M2 macrophages, characterized by elevated Sirt2 expression, permit Mtb growth. Further, we found that HIV-1 augmented Sirt2 gene expression in M[FE]s. Therefore, we explored the therapeutic potential of sirtuin-modulating drugs in M[FE]s. Sirtinol, a Sirt2 inhibitor, significantly reduced HIV-1 growth in M0, M1, and M2-M[FE]s by >1 log10 over 7 days. Conversely, individual doses of resveratrol and SRT1460, which activate Sirt1, did not affect HIV-1. However, their combination showed a strong synergistic inhibition of HIV-1. The combination of sirtinol with resveratrol was neither synergistic nor antagonistic. Sirtinol upregulated iNOS and ATG5 mRNA in HIV-1 infected M[FE]s in a phenotype-dependent manner. In a humanized mouse model (Hu-NSG-SGM3) co-infected with Mtb H37Rv and the HIV-1 BAL strain, treatment with sirtinol alone, or in combination with combination antiretroviral therapy (cART), showed promising results; Sirtinol alone reduced Mtb growth, while its combination with cART effectively inhibited HIV-1 replication in the organs. We propose that Sirt2 blockade and Sirt1-activation represent a novel dual therapeutic strategy for treating HIV-1 and Mtb coinfections.

immunology↗

bioRxiv2024

Lysosomal signalling pathways influence heart rhythm, and regulate atrial function

In the heart, endogenous nicotinic acid adenine dinucleotide phosphate (NAADP) triggers lysosomal calcium (Ca2+) release to augment sarcoplasmic reticulum (SR) Ca2+ sequestration, producing larger Ca2+ transients. However, the role of lysosomal Ca2+ signals in pacemaker activity, a distinct Ca2+-operated function of the sinoatrial node (SAN), or in the atrial myocardium has not been investigated. Pharmacological or genetic ablation of the NAADP pathway inhibits the spontaneous beating rate response to beta-adrenergic stimulation in intact SAN. We found intracellular signaling microdomains between lysosomes and neighboring SR or mitochondria in mouse, and goat tissue. The spatial relationship between lysosomes and other Ca2+-handling organelles are altered in goat atrial fibrillation. Furthermore, we demonstrate atrial myocytes produce cAMP in response to lysosomal signaling, adding a novel trigger for cyclic nucleotide signaling. Our findings support the hypothesis that lysosomal Ca2+ signaling contributes to regulation of cardiomyocyte cAMP levels and pacemaker activity.

physiology↗

bioRxiv2021

Leukocyte adhesion is governed by endolysosomal two pore channel 2 (TPC2)

In response to pro-inflammatory challenges including pathogenic attack and tissue damage, the endothelial cell surface is rearranged to present leukocyte-engaging cell surface receptors. The initial contact needed for leukocyte tethering and rolling is mediated via adhesion demand-driven exocytosis of Weibel-Palade bodies (WPB) that contain the leukocyte receptor P-selectin together with the stabilizing co-factor CD63. We found that diminished expression of the endolysosomal non-selective cation channel TPC2 or inhibition of TPC2-mediated Ca2+-release via trans-Ned 19 led to reduced endolysosomal Ca2+ efflux, and blocked transfer of CD63 from late endosomes/lysosomes (LEL) to WPB, and a concomitant loss of P-selectin on the endothelial cell surface. Accordingly, P-selectin-mediated leukocyte recruitment to trans-Ned 19-treated HUVEC under flow was significantly reduced without disturbing VWF exocytosis. Our findings establish the endolysosome-related TPC2 Ca2+ channel as a key element in the maintenance of proper endothelial functions and a potential pharmacological target in the control of inflammatory leukocyte recruitment.

immunology↗

bioRxiv2020

DFG-1 residue controls inhibitor binding mode and affinity providing a basis for rational design of kinase inhibitor selectivity

ABSTRACTSelectivity remains a challenge for ATP-mimetic kinase inhibitors, an issue that may be overcome by targeting unique residues or binding pockets. However, to date only few strategies have been developed. Here we identify that bulky residues located N-terminal to the DFG motif (DFG-1) represent an opportunity for designing highly selective inhibitors with unexpected binding modes. We demonstrate that several diverse inhibitors exerted selective, non-canonical binding modes that exclusively target large hydrophobic DFG-1 residues present in many kinases including PIM, CK1, DAPK and CLK. Using the CLK family as a model, structural and biochemical data revealed that the DFG-1 valine controlled a non-canonical binding mode in CLK1, providing a rational for selectivity over the closely-related CLK3 which harbors a smaller DFG-1 alanine. Our data suggests that targeting the restricted back pocket in the small fraction of kinases that harbor bulky DFG-1 residues offers a versatile selectivity filter for inhibitor design.Competing Interest StatementThe authors have declared no competing interest.ABBREVIATIONSCLKCdc2 like kinasePIMProviral insertion in murine kinaseACVR1Activin receptor type IDAPKdeath-associated protein kinaseDYRKdual specificity tyrosine-phosphorylation-regulated kinasesDRAKDAP kinase-related apoptosis-inducing protein kinasesCKcasein kinaseRETProto-oncogene tyrosine-protein kinase receptor RetCDK2Cyclin-dependent kinase 2DFG motiftripeptide Asp-Phe-Gly motifVIAK motifvaline-isoleucine-alanine-lysine motif.View Full Text

biochemistry↗