Rsk2 Knockdown in PC12 Cells Results in Sp1 Dependent Increased Expression of the Gria2 Gene, Encoding the AMPA Receptor Subunit GluR2

Tahir Mehmood,Anne Schneider,Solange Pannetier,André Hanauer

doi:10.3390/ijms14023358

Abstract

The RSK2 protein is a member of the RSK serine-threonine protein kinase family and is encoded by the X-linked rps6ka3 gene in human. Highly heterogeneous loss-of-function mutations affecting this gene are responsible for a severe syndromic form of cognitive impairment, Coffin-Lowry syndrome. RSK2, which is highly conserved in mammals, acts at the distal end of the Ras-ERK signaling pathway and is activated in response to growth factors and neurotransmitters. RSK2 is highly expressed in the hippocampus, and Rsk2-KO mice display spatial learning and memory impairment. We recently showed that ERK1/2 activity is abnormally increased in the hippocampus of Rsk2-KO mice as well as the expression of the AMPA receptor subunit GluR2. The mechanism via which RSK2 deficiency affects the expression of GluR2 in neural cells was unknown. To address this issue we constitutively suppressed the expression of RSK2 in PC12 cells via vector-based shRNA in the present study. We show that Rsk2 silencing leads also to an elevation of ERK1/2 phosphorylation as well as of GluR2 expression and that the increased level of GluR2 expression results from the increased ERK1/2 activity on the transcription factor Sp1. Our results provide evidence that RSK2 modulates ERK1/2 activity on Sp1, which regulates GluR2 expression through transcriptional activation.

Highlights

The 90 kDa ribosomal S6 kinases (RSKs) constitute a family of four homologous Ser/Thr kinases (RSK1-4) that are activated by Mitogen activated protein kinase/extracellular-regulated kinases 1 and2 (MAPK/ERK1/2) in response to growth factors, hormones, chemokines and neurotransmitters
We show that Rsk2 silencing in PC12 cells leads to an increase of ERK1/2 activity and of GluR2 expression at the mRNA and protein levels
The recombinant plasmids were transfected into the PC12 cells by lipofectamine 2000, recombinant cells selected 72 h on G418, and mRNA and protein expression levels of the Rsk2 gene were assayed by QRT-PCR and Western blot

Summary

Introduction

The 90 kDa ribosomal S6 kinases (RSKs) constitute a family of four homologous Ser/Thr kinases (RSK1-4) that are activated by Mitogen activated protein kinase/extracellular-regulated kinases 1 and2 (MAPK/ERK1/2) in response to growth factors, hormones, chemokines and neurotransmitters. When activated by Extracellular signal-regulated kinase (ERK), a fraction of RSK2 in turn phosphorylates a number of cytoplasmic substrates such as BCL2-associated agonist of cell death (Bad), p53, L1 cell adhesion molecule (L1CAM) and Glycogen synthase kinase 3 (GSK3) [1]. Another fraction of RSK2 translocates into the nucleus where it is thought to regulate gene expression through phosphorylation of transcription factors such as cAMP-response element binding protein (CREB), the cellular FBJ murine osteosarcoma viral oncogene homolog (c-fos), the oestrogen nuclear receptor, the nuclear receptor subfamily 77 (Nurr 77) and the Activating transcription factor 4 (ATF4) [1,2].

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Results

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