Sée V, Koch B, Loeffler J P
Université Louis Pasteur, UMR 7519 CNRS, Strasbourg Cedex, France.
J Neurochem. 2001 Feb;76(3):778-88. doi: 10.1046/j.1471-4159.2001.00106.x.
The pituitary adenylate cyclase activating polypeptide (PACAP) type I receptor, a seven-domain transmembrane receptor, is positively coupled to both adenylate cyclase and phospholipase C. PACAP exerts neurotrophic effects which are mainly mediated through the cAMP/protein kinase A pathway. Here we show that the cell-permeable C2-ceramide selectively blocks PACAP-activated cAMP production, without affecting phosphoinositide breakdown. Thus by blocking the neuroprotective cAMP signalling pathway, C2-ceramide will reinforce its direct death-inducing signalling. We found that a reactive oxygen species scavenger reversed the C2-ceramide effect and that H2O2 mimicked it. Together these data indicate that reactive oxygen species (ROS) mediates C2-ceramide-induced cAMP pathway uncoupling. This uncoupling did not involve ATP supply or Galphas protein function but rather adenylate cyclase function per se. Further, the tyrosine phosphatase inhibitors, but not the serine/threonine phosphatase inhibitors, prevent inhibition of cAMP production by ROS. This suggests that H2O2 requires a functional tyrosine phosphatase(s) to block PACAP-dependent cAMP production.
垂体腺苷酸环化酶激活多肽（PACAP）I型受体是一种具有七个结构域的跨膜受体，它与腺苷酸环化酶和磷脂酶C均呈正向偶联。PACAP发挥神经营养作用，主要通过cAMP/蛋白激酶A途径介导。在此我们表明，可透过细胞的C2-神经酰胺选择性地阻断PACAP激活的cAMP生成，而不影响磷酸肌醇分解。因此，通过阻断神经保护的cAMP信号通路，C2-神经酰胺将增强其直接诱导死亡的信号传导。我们发现，活性氧清除剂可逆转C2-神经酰胺的作用，且过氧化氢可模拟其作用。这些数据共同表明，活性氧（ROS）介导C2-神经酰胺诱导的cAMP途径解偶联。这种解偶联不涉及ATP供应或Gαs蛋白功能，而是涉及腺苷酸环化酶功能本身。此外，酪氨酸磷酸酶抑制剂而非丝氨酸/苏氨酸磷酸酶抑制剂可防止ROS对cAMP生成的抑制。这表明过氧化氢需要功能性酪氨酸磷酸酶来阻断PACAP依赖的cAMP生成。
