The adipocyte-derived hormone leptin signals the status of body energy stores by activating
the long form of the leptin receptor (LRb). Activation of LRb results in the activation of the
associated Jak2 tyrosine kinase and the transmission of downstream phosphotyrosine-
dependent signals. We have investigated the signaling function of mutant LRb intracellular
domains under the control of the extracellular erythropoietin (Epo) receptor. By using this
system, we confirm that two tyrosine residues in the intracellular domain of murine LRb …