Molecular cloning and characterization of the human glycogen synthase kinase-3 beta promoter

Glycogen synthase kinase 3 beta (GSK-3 beta) is a proline-directed kinase t hat forms part of the wingless signaling pathway. Recent studies have shown that GSK-3 beta phosphorylates the microtubule-associated protein tau in v itro and in cell culture. Tau is the principal component of the paired heli cal filaments (PHFs) found in the brains of patients with Alzheimer disease , and PHF-tau is hyperphosphorylated. GSK-3 beta is therefore one of the ca ndidate kinases for phosphorylating tau in Alzheimer disease. GSK-3 beta ac tivity is negatively regulated by phosphorylation on serine 9 and positivel y regulated by phosphorylation on tyrosine 216. However, since overexpressi on of GSK-3 beta by transfection leads to increased activity in the absence of any stimuli, GSK-3 beta activity may also be regulated at the transcrip tional level. Indeed, increased GSK-3 beta protein levels are found in Alzh eimer disease brains, and GSK-3 beta is found associated with PHFs in Alzhe imer disease. To understand how GSK-3 beta activity may be regulated at the transcriptional level, we have isolated the human GSK-3 beta promoter. The GSK-3 beta promoter does not contain a conventional TATA box although seve ral other transcription factor binding sites were identified. A putative tr anscription start site was mapped by 5' RACE. Transfection of various GSK-3 beta promoter CAT reporter genes into both COS-7 cells and SHSY5Y neuronal cells revealed that the GSK-3 beta promoter is more active in neuronal cel ls. Such transfection studies involving promoter deletion mutants revealed that a negative transcriptional response element may be present at position -1421 to -1363 and an activator sequence at position -427 to -384, CP2 bin ding sites were also present within the promoter, CP2 has recently been sho wn to interact with the Alzheimer disease amyloid precursor protein binding protein Fe65. The significance of these results with respect to Alzheimer disease pathogenesis are discussed. (C) 1999 Academic Press.