Neuropeptide-Y stimulation of extracellular signal-regulated kinases in human erythroleukemia cells

We have used human erythroleukemia (HEL) cells to investigate distal signaling mechanisms of neuropeptide-Y (NPY) receptors. NPY did not activate phospholipase D, determined as a phosphatidylethanol formation, or protein kinase C (PKC) determined enzymatically as a translocation to the plasma membrane. However, NPY caused a rapid (already maximal after 30 s) and concentration-dependent (maximum at 10-100 nM) activation of extracellular signal-regulated kinase (ERK) as assessed by immunoblotting with epitope-specific, antiphosphotyrosine antibodies and in some cases enzymatically. ERK activation by 100 nM NPY was abolished by the Y(1) NPY receptor antagonist BIBP 3226 (1 microM), pertussis toxin treatment (100 ng ml(-1) overnight), the mitogen-activated protein kinase (MAPK) kinase inhibitor PD 98059 (100 microM), and the phosphatidylinositol-3-kinase inhibitor wortmannin (100 nM). Whereas the PKC inhibitor staurosporine (3 microM) inhibited ERK activation by NPY, the chemically distinct PKC inhibitors calphostin C (3 microM), Gö 6976 (3 microM), and bisindolylmaleimide I (3 microM) did not. NPY did not activate other MAPK such as jun N-terminal kinase or p38 MAPK. We conclude that NPY does not activate phospholipase D, PKC, jun N-terminal kinase, or p38 MAPK in HEL cells. However, NPY activates ERK by a pathway involving Y(1) receptors, pertussis toxin-sensitive G proteins, and phosphatidylinositol-3-kinase, whereas PKC may not be involved. Staurosporine may have PKC-independent effects on ERK activation