FIGURE 1.

NGF preferentially increases the rate of formation of PIP3 microdomains in axon segments populated by mitochondria. (A) Examples of the distribution of the TrkA receptor in the membranes of sensory axons as determined by immunostaining with an antibody to the extracellular domain of TrkA under non-permeabilized conditions as in Gallo et al. (1997) and Ketschek and Gallo (2010). (A′) shows an example of an additional axon. Actin filaments were visualized using phalloidin. (B) Example of an NGF treated axon (4–7 min) expressing PH-GFP and with mitochondria labeled using mitochondrially targeted DsRed. At 0 s, representative of 4 min after NGF treatment, a few microdomains are visible as reflected by localized accumulation of PH-GFP. At 35 s a burst of microdomain formation has occurred. The yellow lines denote the positioning of mitochondria relative to the microdomains and define axon segments populated by mitochondria. Note that the majority of microdomains are formed in axon segments populated by mitochondria. (C) Quantification of the rate of microdomain formation per unit length/unit time of axon at 4–6 min after NGF treatment. Mann-Whitney test. (D) Analysis of the rate of microdomain formation in axon segments populated by mitochondria (Mito) and those lacking mitochondria as a function of time after NGF treatment. For each time point after NGF treatment (4–7 min, 1 and 24 h) time matched no NGF treatment control groups are shown. The rate of microdomain formation is normalized to the unit length of micron as mitochondria differ in length and the segments not populated by mitochondria similarly vary in length. The top row of p-values (shorter brackets) report on within NGF treatment group comparing axon segments populated by mitochondria to those that did not. The rest of the p-values report on comparisons within axon segments populated by mitochondria or not and between NGF treatment conditions. Mann-Whitney tests throughout.