Inositol 1,4,5-trisphosphate (IP3) is generally viewed as a global messenger that increases cytosolic calcium ion (Ca2+) concentration. However, the spatiotemporal dynamics of IP3 and the functional significance of localized IP3 production in cell polarity remain largely unknown. Here, we demonstrate the critical role of spatially restricted IP3 signals in axon guidance. We found that IP3 and ensuing Ca2+ signals were produced asymmetrically across growth cones exposed to an extracellular gradient of nerve growth factor (NGF) and mediated growth cone turning responses to NGF. Moreover, photolysisinduced production of IP3 on one side of a growth cone was sufficient to initiate growth cone turning toward the side with the higher concentration of IP3. Thus, locally produced IP3 encodes spatial information that polarizes the growth cone for guided migration.
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