The conserved tyrosine-343 residue on this protein's receptor upregulates the STAT-5 signaling that results after activation of the receptor causes JAK-2 autophosphorylation.  
The conserved tyrosine-343 residue on this protein's receptor upregulates the STAT-5 signaling that results after activation of the receptor causes JAK-2 autophosphorylation.  A low RPI index might indicate a deficiency of this protein. In the absence of this protein, cells at the CFU-E stage undergo apoptosis. Central nervous system tumors known as hemangioblastomas can cause polycythemia by overproducing this protein. In response to hypoxia, HIF-1-alpha promotes the release of this glycoprotein in interstitial cells of the peritubular capillary bed of the (*) kidney. Aranesp and Procrit are "stimulating agents" of this protein illicitly used for blood doping in endurance sports. For 10 points, name this protein that acts at the bone marrow to promote red blood cell formation, or erythropoiesis. 
The conserved tyrosine-343 residue on this protein's receptor upregulates the STAT-5 signaling that results after activation of the receptor causes JAK-2 autophosphorylation.  
erythropoietin [or Epo] 