STAT3 binds phosphotyrosine-1141 of the C-terminal, cytoplasmic region of LEPR (Bjorbaek et al. 1997). Only the long isoform of LEPR has tyrosine-1141 and consequently only the long isoform of LEPR activates STAT3. Short isoforms of LEPR exist but their function is uncertain. Shorter LEPR isoforms bind JAK2 and can signal through IRS-1 or ERKs, including MAPKs (Bjorbaek et al. 1997).