GH receptor (GHR) is a single membrane-spanning glycoprotein dimer that binds GH in its extracellular domain (ECD) GH activates the GHR intracellular domain (ICD)-associated tyrosine kinase, JAK2, which causes intracellular signaling. We previously found that plasma membrane (PM)-associated GHR was dramatically enriched in the lipid raft (LR) component of the membrane and that localization of GHR within PM regions may regulate GH signaling by influencing the profile of pathway activation. In this Study, we examined determinants of LR localization of the GHR using a reconstitution system which lacks endogenous JAK2 and GHR By non-detergent extraction and multistep fractionation, we found that GHR was highly enriched in the LR fraction independent of JAK2 expression. Various GHR mutants were examined in transfectants harboring JAK2 LR concentration was observed for a GHR in which the native transmembrane domain (TMD) is replaced by that of the unrelated LDL receptor and for a GHR that lacks its ICD. Thus, LR association requires neither the TMD nor the ICD. Similarly, a GHR that lacks the ECD, except for the membrane-proximal ECD stem region, was only minimally LR-concentrated. Mutants with internal stern deletions in the context of the full-length receptor were LR-concentrated similar to the wildtype. A GHR lacking ECD subdomain 1 reached the PM and was LR-concentrated, while one lacking ECD subdomain 2, also reached the PM, but was not LR-concentrated These data suggest LR targeting resides in ECD subdomain 2, a region relatively uninvolved in GH binding. (C) 2009 Published by Elsevier Inc.