<p>Sustained Stimulation of β₂AR Inhibits Insulin Signaling in H9C2 Cardiomyoblast Cells Through the PKA-Dependent Signaling Pathway</p>

Abstract

Introduction: This study aimed to investigate the role of β 2 adrenergic receptor (β 2 AR) in insulin signaling transduction in H9C2 cardiomyoblast cells to understand the formation of the β 2 AR-insulin receptor (IR) protein complex and its role in insulin-induced Glut4 expression. Methods: H9C2 cells were treated with various protein inhibitors (CGP, β 1 AR inhibitor CGP20712; ICI, β 2 AR inhibitor ICI 118,551; PKI, PKA inhibitor myristoylated PKI; PD 0325901, MEK inhibitor; SP600125, JNK inhibitor) with or without insulin or isoproterenol (ISO) before RNA-sequencing (RNA-Seq) and quantitative-PCR (Q-PCR). Yeast twohybrid, co-immunoprecipitation and His-tag pull-down assay were carried out to investigate the formation of the β 2 AR-IR protein complex. The intracellular concentrations of cAMP in H9C2 cells were tested by high performance liquid chromatography (HPLC) and the phosphorylation of JNK was tested by Western blot. Results: Gene Ontology (GO) analysis revealed that the most significantly enriched processes in the domain of molecular function (MF) were catalytic activity and binding, whereas in the domain of biological processes (BP) were metabolic process and cellular process. Furthermore, the enriched processes in the domain of cellular components (CC) were cell and cell parts. The Kyoto encyclopedia of genes and genomes (KEGG) pathway analysis showed that the most significant pathways that have been altered included the PI3K-Akt and MAPK signaling pathways. Q-PCR, which was performed to verify the gene expression levels exhibited consistent results. In evaluating the signaling pathways, the sustained stimulation of β 2 AR by ISO inhibited insulin signalling, and the effect was primarily through the cAMP-PKA-JNK pathway and MEK/JNK signaling pathway. Yeast two-hybrid, coimmunoprecipitation and His-tag pull-down assay revealed that β 2 AR, IR, insulin receptor substrate 1 (IRS1), Grb2-associated binding protein 1 (GAB1) and Grb2 existed in the same protein complex. Conclusion: The sustained stimulation of β 2 AR might inhibit insulin signaling transduction through the cAMP-PKA-JNK and MEK/JNK pathways in H9C2 cells.

Attenuation of clinical and immunological outcomes during SARS‐CoV‐2 infection by ivermectin

“…In IVM‐treated hamsters, specifically in females, the term “insulin resistance” was no longer observed in the KEGG enrichment, and the insulin secretion pathway was downregulated. Several other related pathways linking hyperglycemia, inflammation, and lung pathology were downregulated, such as Rap1, AGE‐RAGE, and cGMP‐PKG signaling pathways (Figs EV4 and EV5 ) (Oczypok et al , 2017 ; Pei et al , 2020 ; Isidori et al , 2021 ). In IVM‐treated males, significant modulated pathways determined by KEGG and GO enrichments were related to tight junctions, muscular and epithelial cells (Fig EV4 ).…”

Adrenoceptor Desensitization: Current Understanding of Mechanisms

“…For example, β-AR desensitization or overstimulation is a pathological hallmark of many diseases including asthma, heart failure (HF) (discussed in detail in section 4. Adrenoceptors and Heart failure) and insulin resistance (Mangmool et al, 2018;Pei et al, 2020). Indeed, chronic use of β 2 -AR agonists for acute relief and bronchodilation in asthma leads to functional desensitization or tachyphylaxis in the majority of patients.…”

Current Studies on Molecular Mechanisms of Insulin Resistance

“…Glucose uptake and metabolism as well as fatty acid and protein synthesis are all aided by these intracellular signaling pathways. Binding of IRS with adapter protein Grb2 mediates activation of the ERK pathway which is involved in regulation of genes related to cell survival, cell growth, and differentiation [13]. Ligand-activated IR is internalized and trafficked to early endosome (EE) for dephosphorylation, after which it is degraded or recycled back to the plasma membrane.…”