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Parkin Deficiency Impairs ER-Mitochondria Associations and calcium homeostasis via IP3R-Grp75-VDAC1 Complex

Nai-Jia Xue1, Yi Liu1, Zhi-Hao Lin1

  • 1Department of Neurology, Second Affiliated Hospital, College of Medicine, Zhejiang University, Hangzhou, Zhejiang, 310009, China.

International Journal of Biological Sciences
|January 12, 2026
PubMed

Insights

Parkin regulates calcium transfer at ER-mitochondria contact sites, crucial for Parkinson's disease pathogenesis. Its loss disrupts calcium homeostasis, impacting cell viability and MAM integrity.

Area of Science:

  • Neuroscience
  • Cell Biology
  • Biochemistry

Background:

  • Mitochondria-associated endoplasmic reticulum membranes (MAMs) and calcium homeostasis are implicated in Parkinson's disease (PD).
  • Parkin, an E3 ubiquitin ligase associated with PD, influences MAM integrity and calcium dynamics, but its recruitment and substrate specificity remain unclear.

Purpose of the Study:

  • To elucidate the mechanisms of Parkin recruitment and its role in regulating ER-mitochondria contact sites.
  • To investigate the impact of Parkin deficiency on calcium homeostasis and MAM function in PD pathogenesis.

Main Methods:

  • Investigated Parkin's interaction with the IP3R-Grp75-VDAC1 complex at ER-mitochondria contact sites.
  • Assessed the effects of Parkin loss on ER-mitochondria associations, calcium flux, mPTP opening, and cell viability.
  • Analyzed IP3R levels and Parkin-mediated ubiquitination of IP3R.

Main Results:

  • Loss of Parkin enhances ER-mitochondria associations and leads to excessive calcium flux in MAMs, causing abnormal mPTP opening and reduced cell viability.
  • Parkin physically interacts with the IP3R-Grp75-VDAC1 complex at ER-mitochondria contact sites, being recruited by calcium flux and mitophagy.
  • Parkin deficiency results in IP3R accumulation in MAMs and impairs Parkin's ability to ubiquitinate IP3R for degradation, disrupting calcium transfer regulation.

Conclusions:

  • Parkin plays a critical role in regulating ER-mitochondria contacts and calcium homeostasis by fine-tuning the stability of the IP3R-Grp75-VDAC1 complex.
  • Parkin ubiquitinates IP3R for degradation, ensuring appropriate calcium transfer and maintaining MAM integrity, which is vital for preventing PD pathogenesis.
  • This study reveals a novel function of Parkin in MAMs, offering insights into PD mechanisms and potential therapeutic targets.
Keywords:
IP3RParkincalciummitochondria-associated ER membraneubiquitination

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