Contrasting Functions of Mitogen- and Stress-activated Protein Kinases 1 and 2 in Recognition Memory and In Vivo Hippocampal Synaptic Transmission

MSK1 is required for the beneficial synaptic and cognitive effects of enriched experience across the lifespan

Positive experiences, such as social interaction, cognitive training and physical exercise, have been shown to ameliorate some of the harms to cognition associated with ageing. Animal models of positive interventions, commonly known as environmental enrichment, strongly influence neuronal morphology and synaptic function and enhance cognitive performance. While the profound structural and functional benefits of enrichment have been appreciated for decades, little is known as to how the environment influences neurons to respond and adapt to these positive sensory experiences. We show that adult and aged male wild-type mice that underwent a 10-week environmental enrichment protocol demonstrated improved performance in a variety of behavioural tasks, including those testing spatial working and spatial reference memory, and an enhancement in hippocampal LTP. Aged animals in particular benefitted from enrichment, performing spatial memory tasks at levels similar to healthy adult mice. Many of these benefits, including in gene expression, were absent in mice with a mutation in an enzyme, MSK1, which is activated by BDNF, a growth factor implicated in rodent and human cognition. We conclude that enrichment is beneficial across the lifespan and that MSK1 is required for the full extent of these experience-induced improvements of cognitive abilities, synaptic plasticity and gene expression.

Mitogen- and stress-activated protein kinase (MSK1/2) regulated gene expression in normal and disease states

The mitogen- and stress-activated protein kinases (MSK) are epigenetic modifiers that regulate gene expression in normal and disease cell states. MSK1 and 2 are involved in a chain of signal transduction events bringing signals from the external environment of a cell to specific sites in the genome. MSK1/2 phosphorylate histone H3 at multiple sites, resulting in chromatin remodeling at regulatory elements of target genes and the induction of gene expression. Several transcription factors (RELA of NF-κB and CREB) are also phosphorylated by MSK1/2 and contribute to induction of gene expression. In response to signal transduction pathways, MSK1/2 can stimulate genes involved in cell proliferation, inflammation, innate immunity, neuronal function, and neoplastic transformation. Abrogation of the MSK-involved signaling pathway is among the mechanisms by which pathogenic bacteria subdue the host's innate immunity. Depending on the signal transduction pathways in play and the MSK-targeted genes, MSK may promote or hinder metastasis. Thus, depending on the type of cancer and genes involved, MSK overexpression may be a good or poor prognostic factor. In this review, we focus on mechanisms by which MSK1/2 regulate gene expression, and recent studies on their roles in normal and diseased cells.

MAPK-Activated Protein Kinases: Servant or Partner?

Mitogen-activated protein kinase (MAPK)-activated protein kinases (MAPKAPKs) are defined by their exclusive activation by MAPKs. They can be activated by classical and atypical MAPKs that have been stimulated by mitogens and various stresses. Genetic deletions of MAPKAPKs and availability of highly specific small-molecule inhibitors have continuously increased our functional understanding of these kinases. MAPKAPKs cooperate in the regulation of gene expression at the level of transcription; RNA processing, export, and stability; and protein synthesis. The diversity of stimuli for MAPK activation, the cross talk between the different MAPKs and MAPKAPKs, and the specific substrate pattern of MAPKAPKs orchestrate immediate-early and inflammatory responses in space and time and ensure proper control of cell growth, differentiation, and cell behavior. Hence, MAPKAPKs are promising targets for cancer therapy and treatments for conditions of acute and chronic inflammation, such as cytokine storms and rheumatoid arthritis. Expected final online publication date for the Annual Review of Biochemistry, Volume 91 is June 2022. Please see http://www.annualreviews.org/page/journal/pubdates for revised estimates.