G protein‐coupled receptor kinase 4 gamma‐mediated activation of NF‐κB

Abstract

Polymorphisms within G protein‐coupled receptor kinase 4 gamma (GRK4γ) (R65L, A142V, A486V) are linked to hypertension in epidemiological studies and laboratory studies in mice. However, the mechanistic signal transduction pathway(s) of wild‐type (wt) and polymorphic GRK4γ remains unknown. Recent studies suggest a role of protein‐protein interactions regulating non‐classical roles of GRK4γ, such as interaction with and activation of the NF‐κB cascade. We hypothesized that polymorphic GRK4γ abnormally interacts with, and activates, the NF‐κB cascade. To address this hypothesis molecular modeling and wet lab experiments were conducted to generate models of GRK4γ and elucidate the molecular mechanism underlying GRK4γ activation of NF‐κB. All‐atom molecular dynamics (MD) computer simulation revealed the following shifts in the bundle RH domain from wt GRK4γ: R65L = 6.3 Å, A142V = 1.3 Å, and A486V = 5.1 Å. MD will allow detailed investigation of the conformational dynamics of protein‐protein binding. Luciferase assays containing each NF‐κB promoter indicates only polymorphic GRK4γ increases NF‐κB activity but only in the presence of serum. However, wt and polymorphic GRK4γ interact with NF‐κB essential modulator (NEMO) suggesting that this pathway either requires exogenous activation or is not the only pathway via which GRK4γ can activate NF‐κB. Current studies are designed to examine GRK4γ‐mediated nuclear translocation of each NF‐κB family member as well as the role of IκB and IκK family members. Identification of the structural‐mediated signaling of the polymorphisms may create new directions for personalized hypertension therapy.