Molecular mechanism for the extension of neuronal growth cone : role of exocytosis of integrin.

生长锥上的黏附接触已在多种神经元中被报道，并且被认为是神经突延伸的关键。我们最近证明了神经递质胞分泌与生长锥黏附接触形成之间的密切关系[Tatsumi & Katayama 1999 4371 /id]。当对生长锥施加兴奋性刺激时，细胞底物与生长锥之间的接触也增强了^<49 bb0。这些研究表明，黏附接触与生长锥上的囊泡定位密切相关。为了研究胞涌出与整合素结合到细胞膜的关系，我们用FM4-64（胞涌出的囊泡标记物）和Alexa488标记的抗整合素抗体对细胞进行染色。染色细胞的延时成像显示，大多数囊泡同时含有整合素和FM4-64。对整合素和FM4-64荧光变化的分析表明，胞吐后整合素进入生长锥表面膜，增强了生长锥与底物的接触。

Adhesive contact at a growth cone has been reported in a variety of neurons and is thought to be crucial for neurite extension. We have recently demonstrated a close correlation between exocytosis of neurotransmitters and the formation of adhesive contacts at growth cones {Tatsumi & Katayama 1999 4371 /id}. Contact between a cell substrate and a growth cone was also enhanced when excitatory stimulations are applied to growth cones ^<49>. These studies suggest a close interrelation between an adhesive contact and vesicle localization at the growth cones. To examine the relationship between exocytosis and integrin incorporation into cell membrane, cells were stained with FM4-64 (vesicle marker for exocytosis) and an anti-integrin antibody labeled with Alexa488. Time lapse imaging of the stained cell demonstrated that the majority of vesicles contained both integrins and FM4-64. Analysis of the changes of integrins and FM4-64 fluorescence suggests that incorporation of integrins into the surface membrane of the growth cone after exocytosis, resulting in enhancement of contacts to substrate at growth cones.