Cyclophilin D regulates neuronal activity‐induced filopodiagenesis by fine‐tuning dendritic mitochondrial calcium dynamics

Abstract

Recent studies have highlighted the role of mitochondria in dendritic protrusion growth and plasticity. However, the detailed mechanisms that mitochondria regulate dendritic filopodia morphogenesis remain elusive. Cyclophilin D (CypD, gene name: Ppif) controls the opening of mitochondrial permeability transition pore. Although the pathological relevance of CypD has been intensively investigated, little is known about its physiological function in neurons. Here, we have found that genetic depletion of or pharmaceutical inhibition of CypD blunts the outgrowth of dendritic filopodia in response to KCl-stimulated neuronal depolarization. Further cell biological studies suggest that such inhibitory effect of CypD loss-of-function is closely associated with compromised flexibility of dendritic mitochondrial calcium regulation during neuronal depolarization, as well as the resultant changes in intradendritic calcium homeostasis, calcium signaling activation, dendritic mitochondrial motility and redistribution. Interestingly, loss of CypD attenuates oxidative stress-induced mitochondrial calcium perturbations and dendritic protrusion injury. Therefore, our study has revealed the physiological function of CypD in dendritic plasticity by acting as a fine-tuner of mitochondrial calcium homeostasis. Moreover, CypD plays distinct roles in neuronal physiology and pathology. Cover Image for this issue: doi: 10.1111/jnc.14189.

Caspase inhibition rescues F1Fo ATP synthase dysfunction-mediated dendritic spine elimination

“…Sublethal oligomycin A treatment increases dendritic mitochondrial fragmentation and reduces mitochondrial distribution to spines. Mitochondria are highly dynamic organelles and mitochondrial distribution to dendritic spines is pivotal for spinogenesis and spine function 14,15 . To fully depict the effect of F1Fo ATP synthase inhibition on dendritic mitochondria, we examined mitochondrial dynamics.…”

“…To fully depict the effect of F1Fo ATP synthase inhibition on dendritic mitochondria, we examined mitochondrial dynamics. Mitochondria were determined by particles expressing MitoDsRed 14 . When compared with their counterparts in vehicle-treated neurons, oligomycin A-exposed dendritic mitochondria demonstrated increased numbers ( Fig.…”

“…Mitochondria are dynamic organelles. Mitochondrial morphological control and appropriate positioning are important for neuronal activity and spine remodeling 14,49 . Although the detailed mechanisms of dendritic mitochondrial fragmentation and redistribution in response to F1Fo ATP synthase inhibition require further investigation, we attributed such changes to F1Fo ATP synthase dysfunction-related ATP deficiency, ROS overproduction and mitochondrial Ca 2+ deregulation, which are determined factors affecting mitochondrial dynamics and motility 50 .…”

“…Mitochondria targeted DsRed (Clontech, Mountain View, CA, USA) was inserted into lentivirus vector with human polyubiquitin promoter-C (Addgene, Cambridge, MA, USA). HEK293T cells (ATCC, CRL-3216; RRID: CVCL_0063) were cultured in cell culture medium (DMEM + 10% FBS), one day before transfection, HEK293T cells were sub-cultured into 10 cm dish (Corning) at a density of 6 × 10 6 cells, after 16 h, the cells were transiently co-transfected with packaging vector psPAX2 (Addgene) and envelope vector pMD2.G (Addgene) by using the standard calcium phosphate precipitation method 14 . At 24 h post-transfection, the medium was replaced with fresh DMEM and lentivirus-containing medium was harvested 24 h later.…”

“…After blocking with 5% BSA + 0.2% Triton X-100 (Sigma-Aldrich) for 30 min at room temperature, ActinGreen 488 ReadyProbes Reagent (Life Technologies, R37110) was used to stain F-actin to visualize dendritic protrusions. Images were collected under a Nikon confocal microscope using 40 × Oil Immersion Objective Lens at 0.5 μm thickness of each step size 14 . Dendritic segments between 70 and 100 μm from the soma were used for the analysis.…”