Heat Shock Protein 22 (Hsp22) Regulates Oxidative Phosphorylation upon Its Mitochondrial Translocation with the Inducible Nitric Oxide Synthase in Mammalian Heart

Abstract

ObjectivesStress-inducible heat shock protein 22 (Hsp22) confers protection against ischemia through induction of the inducible isoform of nitric oxide synthase (iNOS). Hsp22 overexpression in vivo stimulates cardiac mitochondrial respiration, whereas Hsp22 deletion in vivo significantly reduces respiration. We hypothesized that Hsp22-mediated regulation of mitochondrial function is dependent upon its mitochondrial translocation together with iNOS.Methods and ResultsAdenoviruses harboring either the full coding sequence of Hsp22 (Ad-WT-Hsp22) or a mutant lacking a N-terminal 20 amino acid putative mitochondrial localization sequence (Ad-N20-Hsp22) were generated, and infected in rat neonatal cardiomyocytes. Compared to β-Gal control, WT-Hsp22 accumulated in mitochondria by 2.5 fold (P<0.05) and increased oxygen consumption rates by 2-fold (P<0.01). This latter effect was abolished upon addition of the selective iNOS inhibitor, 1400W. Ad-WT-Hsp22 significantly increased global iNOS expression by about 2.5-fold (P<0.01), and also increased iNOS mitochondrial localization by 4.5 fold vs β-gal (P<0.05). Upon comparable overexpression, the N20-Hsp22 mutant did not show significant mitochondrial translocation or stimulation of mitochondrial respiration. Moreover, although N20-Hsp22 did increase global iNOS expression by 4.6-fold, it did not promote iNOS mitochondrial translocation.ConclusionTranslocation of both Hsp22 and iNOS to the mitochondria is necessary for Hsp22-mediated stimulation of oxidative phosphorylation.

The valosin‐containing protein is a novel repressor of cardiomyocyte hypertrophy induced by pressure overload

“…Total protein was extracted from LV tissues or cultured NRCMs, and then were measured by Western blotting and detected using the LI‐COR Odyssey ® Infrared Imaging System (LI‐COR Biosciences, Lincoln, NE, USA) as described previously (Qiu et al ., ; Lizano et al ., ; Rashed et al ., ; Zhou et al ., ). GAPDH was used for a loading control of total protein.…”

“…Neonatal rat cardiomyocytes (NRCMs) were isolated and cultured as previously described (Qiu et al ., ; Lizano et al ., ; Rashed et al ., ); 1‐ to 2‐day‐old Sprague Dawley rat pups were euthanized by decapitation and sterilized with alcohol. The NRCMs were then infected with recombined VCP adenovirus (Ad‐VCP) or Ad‐β‐Gal for 24 h as described previously (Lizano et al ., ).…”

Tat-HSP22 inhibits oxidative stress-induced hippocampal neuronal cell death by regulation of the mitochondrial pathway

“…Among HSPs, HSP22 is known as a member of the family of small HSPs containing α-crystal domains, preferentially expressed in heart, and having protective effects against various conditions such as oxidative stress, aging, cancer, and apoptosis [8–11]. Other studies have demonstrated overexpression of HSP22 promotes cardioprotection in an ischemic preconditioning animal model by inhibition of iNOS production and mitochondrial dysfunction [12, 13]. …”

“…Excessive ROS causes damage to macromolecules, subsequently leading to mitochondria dysfunction and cell death [14–16]. Other studies have showed that mitochondrial dysfunction is associated with ROS production and mitochondria as well as with ischemic damage [12–16]. However, the exact biological function and precise mechanism of HSP22 protein in ischemic neuronal damage remains poorly understood.…”

The valosin-containing protein is a novel mediator of mitochondrial respiration and cell survival in the heart in vivo

“…Briefly, RNCMs infected with Ad-β-Gal and Ad-VCP were collected and suspended in extracellular buffer as described1857. Glucose was used as a substrate.…”