Increased Membrane/Nuclear Translocation and Phosphorylation of p90 KD Ribosomal S6 Kinase in the Brain of Hypoxic Preconditioned Mice

Abstract

Our previous studies have demonstrated that hypoxic precondition (HPC) increased membrane translocation of protein kinase C isoforms and decreased phosphorylation of extracellular signal-regulated kinase 1/2 (ERK1/2) in the brain of mice. The goal of this study was to determine the involvement of p90 KD ribosomal S6 kinase (RSK) in cerebral HPC of mice. Using Western-blot analysis, we found that the levels of membrane/nuclear translocation, but not protein expression of RSK increased significantly in the frontal cortex and hippocampus of HPC mice. In addition, we found that the phosphorylation levels of RSK at the Ser227 site (a PDK1 phosphorylation site), but not at the Thr359/Ser363 sites (ERK1/2 phosphorylated sites) increased significantly in the brain of HPC mice. Similar results were confirmed by an immunostaining study of total RSK and phospho-Ser227 RSK. To further define the cellular populations to express phospho-Ser227 RSK, we found that the expression of phospho-Ser227 RSK co-localized with neurogranin, a neuron-specific marker, in cortex and hippocampus of HPC mice by using double-labeled immunofluorescent staining method. These results suggest that increased RSK membrane/nuclear translocation and PDK1 mediated neuron-specific phosphorylation of RSK at Ser227 might be involved in the development of cerebral HPC of mice.

A Pharmacological Activator of AMP-Activated Protein Kinase Protects Hypoxic Neurons in a Concentration-Dependent Manner

“…Ischemic/hypoxic preconditioning is a hypoxia-induced endogenous tolerance to protect cells from injuries caused by subsequent severe hypoxia injury. This phenomenon of protection had been widely observed in many organs and tissues, such as heart and brain [18,19]. Zhang et al employed the ischemic preconditioning model of microvascular endothelial cells (HBMECs) as the vitro model to demonstrate that hypoxic preconditioning inhibited endothelial cells death from apoptotic through the phosphatidylinositol 3-kinase (PI3-kinase)/Akt pathway [20].…”

Glucocorticoid mediates water avoidance stress-sensitized colon-bladder cross-talk via RSK2/PSD-95/NR2B in rats

“…RSK2 is as well implicated in cellular functions (10,11,15,23,36,52) and tumorigenesis (12,33). Although RSK is known to be regulated at the posttranscriptional level by phosphorylation (12,36), it has also been shown that the expression of RSK protein in the frontal cortex is enhanced by hypoxic preconditioning (44) or traumatic stress (54). In this work, we found that daily stress exposure induced dorsal horn RSK2 expression in the dorsal horn of rats.…”

Increased Phosphorylation of Ets-like Transcription Factor-1 in Neurons of Hypoxic Preconditioned Mice

“…It's a suitable ischemic-hypoxic preconditioning model that could be observed clinically. Using this model, we have observed that protein kinase C (PKC) isoforms and its substrate neurogranin (Ng) [18,24,26], cAMP response element binding protein (CREB) [19], ERK1/2 [27], p38 MAPK [22], JNK/SAPK [21], mitogenand stress-activated protein kinase-1 (MSK-1) [20], and p90 KD ribosomal S6 kinase (RSK) [23] were involved in the development of cerebral HPC of mice.…”

“…and perfused transcardially with 0.9% NaCl followed by 4% paraformaldehyde as our previous reports [22,23]. The brains were removed quickly, post-fixed for 24 h in 4% paraformaldehyde and dehydrated in 20% sucrose solution.…”