A New Perspective On The Interaction Between Pre-B Cell Colony Enhancing Factor And Insulin Pathway

Purpose:Pre-B cell colony enhancing factor (PBEF) is a bridge between inflammation and insulin resistance, and a potential target for the research and treatment of inflammation-induced insulin resistance. However, the interaction between PBEF and insulin pathway is highly controversial, and its mechanisms are far from clear. This study looked into the relationship between PBEF, insulin receptor (IR) and insulin pathway from a new perspective-lipid rafts, which revealed a potential mechanism for inflammation induced insulin resistance.Methods:Detergent and detergent-free methods were used to isolate lipid rafts from A549cells, and the distribution of PBEF and IRβ was tested. Recombined PBEF plasmids and its mutant S199were constructed, and PBEF and S199proteins were purified. Cells were given extracellular treatment to study the effect of PBEF on the translocalition of IRβ. Immunoprecipitation (IP) was performed to study the interaction between PBEF, IRβ and Cav-1, as well as phosphorylated Cav-1. The effect of PBEF on insulin-induced Akt activation at different time points was also studied.Results:PBEF was found in both of lipid rafts and non-rafts, while IRP was only found in lipid rafts in detergent-free method. PBEF could induce the movement of IRβ from lipid rafts to non-rafts. NAD had similar effect. This effect could not be blocked by S199or FK866. IRβ, PBEF and Cav-1bound with each other. The tyrosine phosphorylation level of the part of Cav-1that binding with IRβ in non-rafts was higher after PBEF treatment. When adding PBEF within5min following insulin treatment, Akt phosphorylation was inhibited comparing with only giving insulin. However, when adding PBEF after5min following insulin treatment, this effect was partly compromised.Conclusions:1. PBEF was located in both of lipid rafts and non-rafts. PBEF could induce the movement of IRβ from lipid rafts to non-rafts. This effect was partly dependent on its Nampt activity.2. IRβ, PBEF and Cav-lbound with each other. PBEF could induce the co-movement of phosphorylated Cav-1with IRβ into non-rafts, which was dependent on its Nampt activity.3. PBEF could affect insulin-induced Akt phosphorylation, which was time dependent.