VAP spatially stabilizes dendritic mitochondria to locally fuel synaptic plasticity

Ojasee Bapat, Tejas Purimetla, Sarah Kruessel, Christina Thum, Fiona Rupprecht, Monil Shah, Julian D. Langer, Vidhya Rangaraju

Preprint posted on 18 January 2023

A novel player regulating mitochondrial stabilization in the dendrites: A proteomic screen uncovers the role of VAP in tethering mitochondria for continuous fuel supply during synaptic activity.

Selected by Kritika Mehta

Categories: biochemistry, neuroscience


Local information processing in neuronal synapses is energy-intensive and requires a continuous supply of ATP for incurring long-term changes at the synapses1. Making up only 2% of our total body weight, a human brain utilizes about 20% of the body’s total oxygen for its optimal functioning1,2. As shown previously, inhibiting mitochondrial activity blocks protein synthesis-dependent synaptic plasticity3. This observation means that a stable mitochondrial compartment is required at the dendrites to fuel local changes at the synapses in response to synaptic activity.

While the players involved in docking the mitochondria in axonal terminals have been identified and well characterized, the mechanistic basis of mitochondrial tethering and stabilization within neuronal dendrites remains unknown. To address this knowledge gap, the authors of this preprint screened for proteins that exist close to mitochondria and interact with actin and the microtubule cytoskeleton.

Using a knockdown and imaging approach in hippocampal neurons, the authors were able to hone in on the role of the VAP protein – already known to be involved in several neurological diseases4. The authors discovered that the VAPB paralog is particularly localized only to the dendritic compartments. Depletion of VAP from neurons affected the structural plasticity in LTP-induced spines. These findings point to VAP being a major mitochondrial stabilizer near synapses.

Key findings:

To identify the major players in tethering dendritic mitochondria, the authors employed a screening strategy using the APEX tag, which can biotinylate proteins in its vicinity. The APEX tag was targeted to the mitochondrial outer membrane (OMM) and expressed in hippocampal neurons. The captured proteins were identified by mass spectrometry, and the resulting list was filtered for proteins with known interactions with actin and the microtubule cytoskeleton. Eventually, the authors narrowed down to a list of 8 proteins that could be potential players in regulating mitochondrial stability in the dendritic compartments and hence fuel local synaptic plasticity events.

To understand the role of the 8 identified proteins in ensuring dendritic mitochondrial stability and synaptic plasticity, the authors knocked down each of these proteins in hippocampal neurons and measured the actin-mitochondrial interaction in dendrites using Fis1-mCherry and Fis1-Lifeact-GFP. In all knockdown neurons, actin-mitochondrial interaction was significantly reduced in dendrites while unaffected in axons, which suggested a role of these proteins in mitochondrial tethering exclusively to dendritic actin.

To further understand the mechanism by which mitochondrial compartments are stabilized in the dendrites, the authors narrowed their list to three proteins: SNCA, SRGAP2, and VAP. They monitored mitochondrial stability when these proteins were knocked down in hippocampal neurons using photoactivated fluorescence of mitochondria. Knockdown of all three proteins reduced the mitochondrial length at the dendrites. However, of all three knockdowns, only dendrites with VAP knockdown showed a significant decrease in photoactivated mitochondrial compartment fluorescence corresponding to destabilized mitochondrial compartments.

Figure 1 (original fig 6A-B) measuring spine-head width and GCaMP fluorescence before and after synaptic plasticity induction in control and VAP KO hippocampal neurons.

Figure 2 (original fig 6F) Schematic showing VAP as a mitochondrial stabilizer within dendrites supporting synaptic plasticity.

Since VAP is associated with various neurological diseases, the authors then aimed to identify the localization of both paralogs of VAP, VAPA and VAPB, with respect to mitochondria within dendrites and axons. Interestingly, VAPB was specifically enriched near dendritic mitochondria, while VAPA was enriched near dendritic and axonal mitochondria. The specific enrichment of VAPB near dendritic mitochondria made the authors wonder whether VAP protein’s paralog B could be a major stabilizer of dendritic mitochondria and locally support synaptic plasticity. To test this, the authors induced single-spine plasticity using two-photon glutamate uncaging. Spine size was measured in hippocampal neurons with and without VAP knockdown. Interestingly, VAP depletion did not affect the early stages of synaptic plasticity (t=12 mins). However, at later time points (t=22 mins to t=62 mins), spines lacking VAP were unable to retain structural plasticity (increased spine size) (figure 1). Additionally, the ability to exhibit clustered plasticity was also lost in VAP-depleted spines. The authors finally demonstrate a model where VAP tethers and stabilizes dendritic mitochondria, and this spatial stability enables continuous ATP supply via oxidative phosphorylation during synaptic plasticity (see figure 2 above).

What I liked about the preprint:

How a neuron’s intrinsic machinery meets the extensive energy requirements in different compartments is intriguing to me. It is also interesting how different mechanisms exist for mitochondrial stabilization in different neuronal compartments, as loss of each could have diverse but detrimental effects on brain functioning and disease progression. This preprint reflects a significant advancement in our understanding by identifying a critical player facilitating the crucial ATP supply required for long-term synaptic plasticity.

The authors’ approach to identifying new, relevant proteins is impressive to me as this strategy allowed them to screen in a more physiologically relevant model.

Questions to authors:

  1. It is my understanding that VAP brings mitochondria and dendritic actin together. Has domain specificity of VAP for actin and the ER been identified? If yes, is the remaining portion of the VAP protein sufficient for mitochondrial tethering?
  2. Could VAP-associated mitochondria have enhanced stability via the preclusion of the fission-fusion machinery?
  3. As a mitochondrial stabilizer, could VAP be more enriched in active dendrites in comparison to inactive dendrites?

Future Directions:

Studies in the future should focus on validating the role of VAP in stabilizing dendritic mitochondria. Since VAP is enriched in dendrites, it will be interesting to see if only VAP-positive dendritic segments carry mitochondria or if mitochondrial tethering only happens after synaptic activity. Other relevant proteins identified in this preprint should also be explored further for their contribution to dendritic mitochondrial tethering and stabilization.


  1. Mink, J. W., Blumenschine, R. J. & Adams, D. B. Ratio of central nervous system to body metabolism in vertebrates: its constancy and functional basis. American Journal of Physiology-Regulatory, Integrative and Comparative Physiology 241, R203–R212 (1981).
  2. Harris, J. J., Jolivet, R. & Attwell, D. Synaptic Energy Use and Supply. Neuron 75, 762–777 (2012).
  3. Rangaraju, V., Lauterbach, M. & Schuman, E. M. Spatially Stable Mitochondrial Compartments Fuel Local Translation during Plasticity. Cell 176, 73-84.e15 (2019).
  4. Nishimura, A. L. et al. A Mutation in the Vesicle-Trafficking Protein VAPB Causes Late-Onset Spinal Muscular Atrophy and Amyotrophic Lateral Sclerosis. The American Journal of Human Genetics 75, 822–831 (2004).


Posted on: 10 February 2023 , updated on: 13 February 2023

doi: Pending

Read preprint (1 votes)

Author's response

Vidhya Rangaraju shared

  1. It is my understanding that VAP brings mitochondria and dendritic actin together. Has domain specificity of VAP for actin and the ER been identified? If yes, is the remaining portion of the VAP protein sufficient for mitochondrial tethering?

A: VAP is a small ER protein (234 aa) encoded by two genes, VAPA and VAPB. The carboxy-terminal transmembrane domain of VAP is required for its insertion into the ER membrane. Meanwhile, the amino-terminal cytosolic MSP (major sperm protein) domain can bind to FFAT motifs of various proteins, facilitating VAP’s interaction with other organelles, including mitochondria (Guillén-Samander and Camilli 2022). Recently, it has been shown that the coiled-coiled domain of VAP is also required for ER-mitochondria tethering (Mórotz et al., 2022).

  1. Could VAP-associated mitochondria have enhanced stability via the preclusion of the fission-fusion machinery?

A: It is an intriguing possibility. We have not looked at the localization of fission/fusion machinery at the VAP-associated mitochondria-ER contact sites. We will investigate it.

  1. As a mitochondrial stabilizer, could VAP be more enriched in active dendrites in comparison to inactive dendrites?

A: It was recently shown in non-neuronal cells that ER-mitochondria contact sites expand with more VAPB enrichment on acute nutrient starvation (Obara et al. 2022). So, it is possible that dendritic segments that are active and therefore have higher local energy demands, compared to inactive dendrites, might exhibit more enrichment of VAPB at expanded ER-mitochondria contact sites. This local VAPB enrichment and expanded ER-mitochondria contacts are proposed to promote the exchange of metabolites facilitating energy production. We plan to investigate this exciting question using super-resolution microscopy in the future.

Have your say

Your email address will not be published.

This site uses Akismet to reduce spam. Learn how your comment data is processed.

Sign up to customise the site to your preferences and to receive alerts

Register here

preLists in the biochemistry category:

Preprint Peer Review – Biochemistry Course at UFRJ, Brazil

Communication of scientific knowledge has changed dramatically in recent decades and the public perception of scientific discoveries depends on the peer review process of articles published in scientific journals. Preprints are key vehicles for the dissemination of scientific discoveries, but they are still not properly recognized by the scientific community since peer review is very limited. On the other hand, peer review is very heterogeneous and a fundamental aspect to improve it is to train young scientists on how to think critically and how to evaluate scientific knowledge in a professional way. Thus, this course aims to: i) train students on how to perform peer review of scientific manuscripts in a professional manner; ii) develop students' critical thinking; iii) contribute to the appreciation of preprints as important vehicles for the dissemination of scientific knowledge without restrictions; iv) contribute to the development of students' curricula, as their opinions will be published and indexed on the preLights platform. The evaluations will be based on qualitative analyses of the oral presentations of preprints in the field of biochemistry deposited in the bioRxiv server, of the critical reports written by the students, as well as of the participation of the students during the preprints discussions.


List by Marcus Oliveira

CellBio 2022 – An ASCB/EMBO Meeting

This preLists features preprints that were discussed and presented during the CellBio 2022 meeting in Washington, DC in December 2022.


List by Nadja Hümpfer et al.

20th “Genetics Workshops in Hungary”, Szeged (25th, September)

In this annual conference, Hungarian geneticists, biochemists and biotechnologists presented their works. Link:


List by Nándor Lipták


The advances in fibroblast biology preList explores the recent discoveries and preprints of the fibroblast world. Get ready to immerse yourself with this list created for fibroblasts aficionados and lovers, and beyond. Here, my goal is to include preprints of fibroblast biology, heterogeneity, fate, extracellular matrix, behavior, topography, single-cell atlases, spatial transcriptomics, and their matrix!


List by Osvaldo Contreras

ASCB EMBO Annual Meeting 2019

A collection of preprints presented at the 2019 ASCB EMBO Meeting in Washington, DC (December 7-11)


List by Madhuja Samaddar et al.

EMBL Seeing is Believing – Imaging the Molecular Processes of Life

Preprints discussed at the 2019 edition of Seeing is Believing, at EMBL Heidelberg from the 9th-12th October 2019


List by Dey Lab

Cellular metabolism

A curated list of preprints related to cellular metabolism at Biorxiv by Pablo Ranea Robles from the Prelights community. Special interest on lipid metabolism, peroxisomes and mitochondria.


List by Pablo Ranea Robles


This list of preprints is focused on work expanding our knowledge on mitochondria in any organism, tissue or cell type, from the normal biology to the pathology.


List by Sandra Franco Iborra