Alpha herpesvirus exocytosis from neuron cell bodies uses constitutive secretory mechanisms, and egress and spread from axons is independent of neuronal firing activity
Fig 1
PRV particles use constitutive secretory pathway to exit from the cell body of primary SCG neurons.
(A) PRV particles (mCherry-VP26 capsid tag) colocalize with EmGFP-Rab6a in the cell body of SCG neurons. Colocalization quantified from 40 cells over 5 independent experiments. Pearson’s correlation between red and green channels was significantly greater (p<0.01, student’s t-test) at intracellular membranes compared to control conditions. Scale bar represents 4 μm. (B) PRV particles and EmGFP-Rab6a co-transport in the cell body. Kymograph represents particle movement along the indicated track (magenta). Data are representative of >56 cells over 7 independent experiments. Scale bar represents 4 μm. (C) Virus particle exocytosis from neuron cell bodies occurs as early as 5 hpi. Image is a maximum difference projection over a 5.3 min time course. Exocytosis of gM-pHluorin particles that do not contain capsids (green circles) and particles containing both gM-pHluorin and capsids (yellow circles) are indicated. Scale bar represents 4 μm. (D) Ensemble average of gM-pHluorin fluorescence (green line) and mRFP capsid (red line) over 26 exocytosis events. Shaded area represents standard deviation. (E-F) SCG neurons were transduced to express mCherry-Rab proteins, infected with PRV expressing gM-pHluorin, and imaged beginning at 5 hr after PRV infection. Images show representative exocytosis events at the moment of exocytosis (time = 0). Each image is 5 μm square. Line plots are ensemble averages of gM-pHluorin (top, green line) and mCherry-Rab protein (bottom, red line) relative fluorescence. Shaded area represents standard deviation. (E) Rab6a is associated with virus particle exocytosis from neuron cell bodies. Data represent 72 exocytosis events. (F) Rab8a is associated with virus particle exocytosis from neuron cell bodies. Data represent 35 exocytosis events.