Working model. HDL-mediated cholesterol efflux from MkPs via ABCG4 increases activity of the palmitoylated Lyn kinase, c-CBL phosphorylation and activation, and c-MPL degradation, limiting MkP proliferation and platelet production. JAK2, Janus kinase 2; P, phosphate; pY, phosphotyrosine; STAT, signal transducer and activator of transcription.