Autophagy inhibition rescues structural and functional defects caused by the loss of mitochondrial chaperone <i>Hsc70-5</i> in <i>Drosophila</i>

We investigated in larval and adult <i>Drosophila</i> models whether loss of the mitochondrial chaperone <i>Hsc70-5</i> is sufficient to cause pathological alterations commonly observed in Parkinson disease. At affected larval neuromuscular junctions, no effects on terminal size, bouton size or number, synapse size, or number were observed, suggesting that we studied an early stage of pathogenesis. At this stage, we noted a loss of synaptic vesicle proteins and active zone components, delayed synapse maturation, reduced evoked and spontaneous excitatory junctional potentials, increased synaptic fatigue, and cytoskeleton rearrangements. The adult model displayed ATP depletion, altered body posture, and susceptibility to heat-induced paralysis. Adult phenotypes could be suppressed by knockdown of <i>dj-1β, Lrrk, DCTN2-p50, DCTN1-p150, Atg1, Atg101, Atg5, Atg7</i>, and <i>Atg12</i>. The knockdown of components of the macroautophagy/autophagy machinery or overexpression of human <i>HSPA9</i> broadly rescued larval and adult phenotypes, while disease-associated <i>HSPA9</i> variants did not. Overexpression of <i>Pink1</i> or promotion of autophagy exacerbated defects. <b>Abbreviations:</b> AEL: after egg laying; AZ: active zone; brp: bruchpilot; Csp: cysteine string protein; dlg: discs large; eEJPs: evoked excitatory junctional potentials; GluR: glutamate receptor; H₂O₂: hydrogen peroxide; mEJP: miniature excitatory junctional potentials; MT: microtubule; NMJ: neuromuscular junction; PD: Parkinson disease; <i>Pink1</i>: PTEN-induced putative kinase 1; PSD: postsynaptic density; SSR: subsynaptic reticulum; SV: synaptic vesicle; VGlut: vesicular glutamate transporter.