Role of CREB in the regulatory action of sarsasapogenin on muscarinic M₁ receptor density during cell aging

Abstract 

This work studied the role of cyclic AMP responsive element binding protein (CREB) in the up-regulation of M₁ muscarinic acetylcholine receptor (M₁ receptor) density by sarsasapogenin (ZMS) in CHO cells transfected with M₁ receptor gene (CHOm1 cells). During cell aging, sarsasapogenin elevated M₁ receptor density as well as CREB and phosphor-CREB (pCREB) levels. CREB peaked earliest, followed by pCREB and M₁ receptor density peaked last. When CREB synthesis was blocked by antisense oligonucleotides, the elevation effect of sarsasapogenin on M₁ receptor density was abolished. These results suggest that sarsasapogenin up-regulates M₁ receptor density in aged cells by promoting CREB production and phosphorylation. Furthermore, the results support the hypothesis that pCREB regulates M₁ receptor gene expression through heterodimer formation.

Abbreviations: CREB, cyclic AMP responsive element binding protein, CRE, cyclic AMP responsive element, pCREB, phosphor-CREB, CBP, CREB-binding protein, M receptor, muscarinic acetylcholine receptor, M₁ receptor, muscarinic receptor subtype 1, ZMS, sarsasapogenin, DMSO, dimethylsulfoxide, CHOm1 cell line, CHO cells transfected with M₁ receptor gene, SDS, sodium dodecyl sulfate, PVDF, polyvinylidene difluoride, AP-1, activator protein-1, BDNF, brain derived neurotrophic factor, ERK, extracellular signal-regulated kinase, MAPK, mitogen-activated protein kinase

Keywords: Sarsasapogenin (ZMS), Cyclic AMP response element binding protein (CREB), Phosphorylated CREB (pCREB), Antisense oligonucleotide, Muscarinic acetylcholine receptor subtype 1 (M₁ receptor), CHO cells transfected with M₁ receptor gene (CHOm1 cell)