The mitochondrial-derived peptide humanin activates the ERK1/2, AKT, and STAT3 signaling pathways and has age-dependent signaling differences in the hippocampus
ONCOTARGET
Authors: Kim, Su-Jeong; Guerrero, Noel; Wassef, Gabriella; Xiao, Jialin; Mehta, Hemal H.; Cohen, Pinchas; Yen, Kelvin
Abstract
Humanin is a small secreted peptide that is encoded in the mitochondrial genome. Humanin and its analogues have a protective role in multiple age-related diseases including type 2 diabetes and Alzheimer's disease, through cytoprotective and neuroprotective effects both in vitro and in vivo. However, the humanin-mediated signaling pathways are not well understood. In this paper, we demonstrate that humanin acts through the GP130/IL6ST receptor complex to activate AKT, ERK1/2, and STAT3 signaling pathways. Humanin treatment increases phosphorylation in AKT, ERK 1/2, and STAT3 where PI3K, MEK, and JAK are involved in the activation of those three signaling pathways, respectively. Furthermore, old mice, but not young mice, injected with humanin showed an increase in phosphorylation in AKT and ERK1/2 in the hippocampus. These findings uncover a key signaling pathway of humanin that is important for humanin's function and also demonstrates an age-specific in vivo effect in a region of the brain that is critical for memory formation in an age-dependent manner.
Lymphocyte DNA methylation mediates genetic risk at shared immune-mediated disease loci
JOURNAL OF ALLERGY AND CLINICAL IMMUNOLOGY
Authors: Clark, Alexander D.; Nair, Nisha; Anderson, Amy E.; Thalayasingam, Nishanthi; Naamane, Najib; Skelton, Andrew J.; Diboll, Julie; Barton, Anne; Eyre, Stephen; Isaacs, John D.; Pratt, Arthur G.; Reynard, Louise N.
Abstract
Background: Defining regulatory mechanisms through which noncoding risk variants influence the cell-mediated pathogenesis of immune-mediated disease (IMD) has emerged as a priority in the post-genome-wide association study era. Objectives: With a focus on rheumatoid arthritis, we sought new insight into genetic mechanisms of adaptive immune dysregulation to help prioritize molecular pathways for targeting in this and related immune pathologies. Methods: Whole-genome methylation and transcriptional data from isolated CD4(+) T cells and B cells of more than 100 genotyped and phenotyped patients with inflammatory arthritis, all of whom were naive to immunomodulatory treatments, were obtained. Analysis integrated these comprehensive data with genome-wide association study findings across IMDs and other publicly available resources. Results: We provide strong evidence that disease-associated DNA variants regulate cis-CpG methylation in CD4(+) T and/or B cells at 37% RA loci. Using paired, cell-specific transcriptomic data and causal inference testing, we identify examples where site-specific DNA methylation in turn mediates gene expression, including FCRL3 in both cell types and ORMDL3/GSDMB, IL6ST/ANKRD55, and JAZF1 in CD4(+) T cells. A number of genes regulated in this way highlight mechanisms common to RA and other IMDs including multiple sclerosis and asthma, in turn distinguishing them from osteoarthritis, a primarily degenerative disease. Finally, we corroborate the observed effects experimentally. Conclusions: Our observations highlight important mechanisms of genetic risk in RA and the wider context of immune dysregulation. They confirm the utility of DNA methylation profiling as a tool for causal gene prioritization and, potentially, therapeutic targeting in complex IMD.