title: Cognitive impairment in Coffin-Lowry syndrome correlates with reduced RSK2 activation.
abstract: BACKGROUND
  Gene expression and protein synthesis, mediated by the transcription factor CREB (cAMP response element binding protein), play an important role in learning and memory in several species, including Drosophila, snails, and mice. Patients with the X-linked disorder Coffin-Lowry syndrome (CLS) have cognitive disabilities, distinctive features, and bony abnormalities as well as mutations in RSK2 (ribosomal S6 kinase-2), a protein kinase that activates CREB by phosphorylation at serine 133. In fibroblasts from a single patient with CLS, epidermal growth factor (EGF)-stimulated CREB phosphorylation was reduced.
  
  
  METHODS
  The authors assessed endogenous CREB phosphorylation in a CLS fibroblast line by Western blotting and found impaired CREB phosphorylation in response to stimulation by EGF and the protein kinase C (PKC) agonist phorbol 12-myristate 13-acetate (PMA). They studied RSK2 immunoprecipitated from fibroblasts and lymphoblasts from seven patients with CLS and found a wide range in RSK2's capacity to phosphorylate the synthetic CREB-like peptide, CREBtide, after cell stimulation by PMA.
  
  
  RESULTS
  In lymphoblasts from patients with CLS, PMA-stimulated CREBtide phosphorylation was increased 1.2- to 2.7-fold over baseline, compared to an average fourfold increase in controls. Regression analysis suggested a linear relationship between the magnitude of in vitro RSK2-mediated CREBtide phosphorylation and CLS patient intelligence level (p < 0.05).
  
  
  CONCLUSIONS
  This report suggests a correlation between human cognitive performance and cellular capacity to activate RSK2. It provides additional evidence that the CREB kinase, RSK2, and CREB phosphorylation may play important roles in human learning and memory, as they do in lower animals.
authors.affiliation: Kennedy Krieger Institute, Baltimore, MD, USA. Harum@kennedykrieger.org
authors.forename: K H
authors.initials: KH
authors.lastname: Harum
authors.forename: L
authors.initials: L
authors.lastname: Alemi
authors.forename: M V
authors.initials: MV
authors.lastname: Johnston
mesh_terms: D000015:Abnormalities, Multiple / Q000201:enzymology* / Q000503:physiopathology; D002648:Child; D002675:Child, Preschool; D003072:Cognition Disorders / Q000201:enzymology* / Q000503:physiopathology; D017362:Cyclic AMP Response Element-Binding Protein / Q000378:metabolism; D005260:Female; D006801:Humans; D007223:Infant; D008607:Intellectual Disability / Q000201:enzymology* / Q000503:physiopathology; D008297:Male; D019893:Ribosomal Protein S6 Kinases / Q000378:metabolism*; D013577:Syndrome; D014960:X Chromosome
chemical_list: D017362:Cyclic AMP Response Element-Binding Protein; D019893:Ribosomal Protein S6 Kinases