Bixby J L, Grunwald G B, Bookman R J
Department of Molecular & Cellular Pharmacology, University of Miami School of Medicine, Florida 33136.
J Cell Biol. 1994 Dec;127(5):1461-75. doi: 10.1083/jcb.127.5.1461.
The signaling mechanisms underlying neurite growth induced by cadherins and integrins are incompletely understood. In our experiments, we have examined these mechanisms using purified N-cadherin and laminin (LN). We find that unlike the neurite growth induced by fibroblastic cells expressing transfected N-cadherin (Doherty, P., and F.S. Walsh. 1992. Curr. Opin. Neurobiol. 2:595-601), growth induced by purified N-cadherin in chick ciliary ganglion (CG), sensory, or forebrain neurons is not sensitive to inhibition by pertussis toxin. Using fura-2 imaging of single cells, we show that soluble N-cadherin induces Ca2+ increases in CG neuron cell bodies, and, importantly, in growth cones. In contrast, N-cadherin can induce Ca2+ decreases in glial cells. N-cadherin-induced neuronal Ca2+ responses are sensitive to Ni2+, but are relatively insensitive to diltiazem and omega-conotoxin. Similarly, neurite growth induced by purified N-cadherin is inhibited by Ni2+, but is unaffected by diltiazem and conotoxin. Soluble LN also induced small Ca2+ responses in CG neurons. LN-induced neurite growth, like that induced by N-cadherin, is insensitive to diltiazem and conotoxin, but is highly sensitive to Ni2+ inhibition. K+ depolarization experiments suggest that voltage-dependent Ca2+ influx pathways in CG neurons (cell bodies and growth cones) are largely blocked by the combination of diltiazem and Ni2+. Our results demonstrate that cadherin signaling involves cell type-specific Ca2+ changes in responding cells, and in particular, that N-cadherin can cause Ca2+ increases in neuronal growth cones. Our findings are consistent with the current idea that distinct neuronal transduction pathways exist for cell adhesion molecules compared with integrins, but suggest that the involvement of Ca2+ signals in both of these pathways is more complex than previously appreciated.
钙黏蛋白和整合素诱导神经突生长的信号传导机制尚未完全明确。在我们的实验中，我们使用纯化的N-钙黏蛋白和层粘连蛋白（LN）研究了这些机制。我们发现，与表达转染N-钙黏蛋白的成纤维细胞诱导的神经突生长不同（多尔蒂，P.，和F.S.沃尔什。1992年。《当代神经生物学观点》2:595-601），纯化的N-钙黏蛋白在鸡睫状神经节（CG）、感觉神经元或前脑神经元中诱导的生长对百日咳毒素的抑制不敏感。通过单细胞fura-2成像，我们发现可溶性N-钙黏蛋白可诱导CG神经元胞体中Ca2+增加，重要的是，也可诱导生长锥中Ca2+增加。相比之下，N-钙黏蛋白可诱导神经胶质细胞中Ca2+减少。N-钙黏蛋白诱导的神经元Ca2+反应对Ni2+敏感，但对地尔硫䓬和ω-芋螺毒素相对不敏感。同样，纯化的N-钙黏蛋白诱导的神经突生长受到Ni2+抑制，但不受地尔硫䓬和芋螺毒素影响。可溶性LN也可在CG神经元中诱导小的Ca2+反应。LN诱导的神经突生长，与N-钙黏蛋白诱导的一样，对地尔硫䓬和芋螺毒素不敏感，但对Ni2+抑制高度敏感。K+去极化实验表明，CG神经元（胞体和生长锥）中电压依赖性Ca2+内流途径在很大程度上被地尔硫䓬和Ni2+的组合所阻断。我们的结果表明，钙黏蛋白信号传导涉及反应细胞中细胞类型特异性的Ca2+变化，特别是，N-钙黏蛋白可导致神经元生长锥中Ca2+增加。我们的发现与当前的观点一致，即与整合素相比，细胞黏附分子存在不同的神经元转导途径，但表明这两种途径中Ca2+信号的参与比以前认为的更为复杂。
