Journal: The Journal of Cell Biology

Article Title: Hsc70 chaperone activity is required for the cytosolic slow axonal transport of synapsin

doi: 10.1083/jcb.201604028

Figure Lengend Snippet: Inactivation of Hsc70 ATPase activity blocks slow axonal transport and presynaptic accumulation of synapsin. (A) Schematic of assay to determine slow axonal transport of synapsin using photoactivatable synapsin (PAGFP:synapsin; ; ). In brief, PAGFP:synapsin was photoactivated in a discrete axonal ROI, and the fluorescence was tracked over time by live imaging. (B) Kymographs from photoactivation experiments in A. Note the anterogradely biased dispersion of PAGFP:synapsin fluorescence in control axons, thought to represent slow transport (midpoint of photoactivated zone marked by red arrowhead and dashed line; top). Also note that the Hsc70 inhibitor (100 µM VER155008; bottom) eliminated the anterograde bias. (C) Quantification of the transport experiments. In brief, the centroid of the photoactivated zone was quantified in each image of a given time-lapse video, and the displacement of the centroid was quantified over time (intensity center shift; ). Note that although the population of photoactivated synapsin was transported anterogradely, pharmacologic (VER155008) or genetic (DN-Hsc70) inactivation of Hsc70 ATPase activity prevented the biased transit. (D) Attenuation of endogenous synapsin levels at presynaptic boutons upon selective inactivation of Hsc70 in axons. Axons and presynaptic boutons were isolated from somatodendritic compartments using a triple-chamber microfluidic device (see Fig. S1 for design of device). Thereafter, the Hsc70 inhibitor VER155008 (or DMSO control) was selectively added to the axonal/presynaptic chamber, and the neurons were fixed and immunostained with anti-VAMP2 (to detect all presynapses; green) and anti-synapsin (red) antibodies. Representative images from axonal/presynaptic chambers are shown. (E) Quantification of colocalization between synapsin and VAMP2. Note that Hsc70 inactivation significantly attenuated the presynaptic localization of synapsin. Error bars show means ± SEM. **, P < 0.01.

Article Snippet: VER155008 was used as the Hsc70 inhibitor (3803; Tocris Bioscience).

Techniques: Activity Assay, Fluorescence, Imaging, Dispersion, Control, Isolation

Journal: The Journal of Cell Biology

Article Title: Hsc70 chaperone activity is required for the cytosolic slow axonal transport of synapsin

doi: 10.1083/jcb.201604028

Figure Lengend Snippet: Inactivation of Hsc70 ATPase activity leads to disruption of axonal synapsin. (A) Strategy to analyze the fluorescence decay of PAGFP:synapsin in an axon ROI over time. PAGFP:synapsin was photoactivated in a discrete axonal ROI, and the dispersion of fluorescence was quantified over time. (B) Fluorescence decay of PAGFP:synapsin in axon ROIs. Note faster decay of fluorescence upon Hsc70 inactivation. (C) Representative images showing endogenous distribution of synapsin in axons upon pharmacologic and genetic Hsc70 inactivation (VER155008 and Hsc70-DN). Note that the punctate distribution is disrupted upon Hsc70 inhibition. (D) Quantification of the periodicity of axonal synapsin particles with or without Hsc70 inactivation. Periodicity of endogenous synapsin particles (i.e., distances between adjacent puncta) was determined from axonal line scans, as shown in the example (top left; red boxed region from C). Cumulative data from control axons is shown on the top right, represented by FFTs (see the Colocalization analysis of widefield images… section of Materials and methods for details). Note the major peak at ∼2.77 µm, representing the typical spacing of synapsin puncta in control axons (dashed line over minor peaks). Also note loss of the major peak upon Hsc70 inhibition, reflecting disruption of the periodic synapsin distribution in axons. (E) HEK293 cells were transfected with GFP:synapsin, immunoprecipitated with an anti-GFP antibody, and blotted with anti-GFP and anti-Hsc70 antibodies (with or without VER155008). Note that addition of the Hsc70 inhibitor led to a significant reduction in the amount of immunoprecipitated Hsc70. Molecular mass is shown in kilodaltons. (F) Quantification of blots in E. n = 3 separate experiments. Error bars show means ± SEM. **, P < 0.01.

Article Snippet: VER155008 was used as the Hsc70 inhibitor (3803; Tocris Bioscience).

Techniques: Activity Assay, Disruption, Fluorescence, Dispersion, Inhibition, Control, Transfection, Immunoprecipitation