GH binds to the GHR dimer, which undergoes internal rotation, resulting in JAK2 phosphorylation (P) and subsequent signal transduction. GH signaling is mediated by JAK2 phosphorylation of depicted signaling molecules or by JAK2-independent signaling including Src/ERK pathways (S42). Ligand binding to a preformed GHR dimer results in internal rotation and subsequent phosphorylation cascades. GH targets include IGF-I, c-fos, cell proliferation genes, glucose metabolism, and cystoskeletal proteins. GHR internalization and translocation (dotted lines) induce nuclear proproliferation genes via importin α/β (Impα/Impβ) coactivator (CoAA) signaling. IGF-I may also block GHR internalization, acting in a feedback loop. The GHR antagonist, pegvisomant, blocks GHR signaling; SRLs also attenuate GH binding and signaling (not shown).