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

生长锥处的粘附性接触已在多种神经元中被报道，并且被认为对神经突延伸至关重要。我们最近已经证明了神经递质的胞吐作用与生长锥处粘附接触的形成之间的密切相关性{Tatsumi & Katayama 1999 4371 /id}。当对生长锥施加兴奋性刺激时，细胞基质和生长锥之间的接触也得到增强<49>。这些研究表明，在生长锥的粘附接触和囊泡定位之间的密切相关性。为了检查胞吐作用和整合素掺入细胞膜之间的关系，用FM 4 -64（胞吐作用的囊泡标记物）和用Alexa 488标记的抗整合素抗体对细胞进行染色。染色细胞的时间推移成像表明，大多数囊泡含有整联蛋白和FM 4 -64。整合素和FM 4 -64荧光的变化的分析表明，整合素的掺入到细胞外分泌后的生长锥的表面膜，导致在生长锥与底物的接触增强。

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.