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Signal transduction and exercise
Published in Adam P. Sharples, James P. Morton, Henning Wackerhage, Molecular Exercise Physiology, 2022
Brendan Egan, Adam P. Sharples
In Step 3, the exercise stimulus, consequent homoeostatic perturbations and associated signals interact with cellular sensors resulting in the activation and/or repression of signal transduction pathways that amplify and/or dampen the initial signals. Much of the focus of research on this step has been on ‘classical’ signal transduction (i.e. protein-protein interactions, posttranslational modifications such as phosphorylation and acetylation, and protein translocation), particularly as it relates to modulating the activities of downstream transcriptional and translational regulators (Figure 7.3) (8, 9, 14). These regulators, or effector proteins, and their associated processes, constitute Step 4 of the model as described below. Prior to that discussion, given that signal transduction is the ‘engine room’ of the model, it is pertinent to describe to classical features of intracellular signal transduction in more detail.
Stress Proteins in Renal Ischemia
Published in John J. Lemasters, Constance Oliver, Cell Biology of Trauma, 2020
HSP 70 is a large family with both constitutive (HSC 70-heat shock cognate) and inducible members. In a review, Pelham suggested that heat shock proteins may mediate assembly processes but they may also promote disassembly of proteins damaged because of stress. In the case of HSP 70, he suggested that HSP 70 binds to hydrophobic regions of proteins, either in a normal process (e.g., unfolding during protein translocation across membranes) or in denaturation (e.g., protein damage after ischemia).7 Physical measurements by Palleros et al., showed that HSP 70 binds to unfolded proteins but not folded proteins.51
Engineering Escherichia coli to Combat Cancer
Published in Ananda M. Chakrabarty, Arsénio M. Fialho, Microbial Infections and Cancer Therapy, 2019
Carlos Piñero-Lambea, David Ruano-Gallego, Gustavo Bodelón, Beatriz Álvarez, Luis Ángel Fernández
We also demonstrated that SIEC was capable of protein translocation into mammalian cells. As a first approach, we measured the formation of the EspB/D translocation pore in the plasma membrane by quantifying the lysis of red blood cells by bacteria [91]. This assay had been previously used to quantitate the assembly of functional injectisomes by EPEC strains [102]. The hemolytic activity determined for the induced SIEC strain reached ca. 70% of that detected with wild-type EPEC, indicating that EspB and EspD translocators secreted by SIEC were capable of forming pores on mammalian plasma membranes.
Helicobacter pylori employs a general protein glycosylation system for the modification of outer membrane adhesins
Published in Gut Microbes, 2022
Kai-Wen Teng, Kai-Siang Hsieh, Ji-Shiuan Hung, Chun-Jen Wang, En-Chi Liao, Pei-Chun Chen, Ying-Hsuan Lin, Deng-Chyang Wu, Chun-Hung Lin, Wen-Ching Wang, Hong-Lin Chan, Shau-Ku Huang, Mou-Chieh Kao
By performing subcellular fractionation and immunoblotting, we identified that the molecular sizes of all tested adhesins displayed a two-step upshift pattern from the cytoplasm to the outer membrane, indicating that the glycosylation process of these adhesins may occur during or immediately after protein transport across the inner membrane. Studies have suggested that protein N-linked glycosylation in bacteria occurs before complete folding of substrate proteins and is a co-translocation process during protein translocation across the inner membrane.32 The gradual upshift patterns of adhesins observed in this study imply that they are simultaneously transported to the periplasm and modified by glycans. Therefore, a reasonable hypothesis is that adhesins present in the outer membrane fraction are the complete glycosylated form of adhesins, while those observed in the inner membrane fraction are still undergoing the glycosylation process and considered semi-glycosylated adhesins. However, another possible interpretation that cannot be completely excluded is the presence of a second glycosylation system in the periplasm that is yet to be identified and will complete the glycosylation process for these adhesins. Further studies are required to differentiate the two assumptions described above and reveal the detailed mechanism of adhesin glycosylation in H. pylori.
Endoplasmic reticulum stress mediates parathyroid hormone-induced apoptosis in vascular smooth muscle cells
Published in Renal Failure, 2022
Shuzhong Duan, Xinpan Chen, Yingjie Liu, Weikang Guo, Wenhu Liu
The ER is an essential organelle that participates in protein quality control of all eukaryotic cells. ER homeostasis is critical to control various intracellular physiological functions including protein folding, protein translocation, lipid metabolism, cell differentiation, and calcium homeostasis [7]. There are three main branches of ER stress: inositol-requiring enzyme 1α (IRE1α), PRK-like ER kinase (PERK), and activating transcription factor (ATF) 6. When the ER is operating under homeostatic conditions, IRE1α, PERK, and ATF6 are kept in monomeric and inactive states through interactions with an ER chaperone called 78-kDa glucose-regulated protein/immunoglobulin-binding protein (GRP78/BiP). However, under many pathological conditions, misfolded proteins accumulate in the ER to an unmanageable level, which activates IRE1α, PERK, or ATF6 to induce ER stress. When the pathological condition is short and reversible, ER stress can save the cell fate. However, if cellular damage persists and induces chronic ER stress, cells trigger the apoptosis pathway. ER stress-induced apoptosis is mainly mediated through PERK and IRE1 pathways. PERK activates a prosurvival mechanism, but switches to a proapoptotic mechanism under prolonged ER stress by regulating ATF4 and CAAT/enhancer-binding protein homologous protein (CHOP). IRE1 activates the c-Jun N-terminal kinase (JNK) pathway that ultimately triggers apoptosis [8,9]. Capase-12 localized to the ER and activated by ER stress has been identified to mediate ER stress-induced apoptosis [10,11].
Methylglyoxal stimulates endoplasmic reticulum stress in vascular smooth muscle cells
Published in Journal of Receptors and Signal Transduction, 2022
Newly synthesized and secretory membrane proteins are transferred to the ER for modification [7]. If the unfolded protein response (UPR) system could not remove the unfolded/misfolded proteins from the ER lumen, ER stress is induced. Upon ER stress induction, new protein translocation to the ER is reduced, retrotranslocation, protein degradation, and the ER’s folding capacity are augmented [8]. In the case ER stress is not relieved, it may become lethal for the cell. UPR is a planned, complex system and composed of three ER transmembrane receptor proteins: PERK (double-stranded RNA-activated protein kinase-like endoplasmic reticulum kinase), IRE1 (inositol-requiring enzyme-1), and ATF6 (activating transcription factor 6). Studies have shown that ER stress participates in atherosclerosis and cardiovascular diseases [7,9].