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Overexpressed p32 localized in the endoplasmic reticulum and mitochondria negatively regulates calcium‑dependent

Kwanhoon Choi1, Bon-Hyeock Koo2, Byeong Jun Yoon2

  • 1Department of Anesthesiology and Pain Medicine, Yonsei University Wonju College of Medicine, Wonju, Gangwon 26426, Republic of Korea.

Molecular Medicine Reports
|July 25, 2020
PubMed

Insights

The p32 protein regulates calcium levels in cells, impacting signaling pathways. Increased p32 causes endothelial dysfunction by disrupting calcium balance and reducing nitric oxide production, suggesting it as a target for vascular diseases.

Area of Science:

  • Cellular Biology
  • Cardiovascular Research
  • Biochemistry

Background:

  • The p32 protein is involved in regulating cytosolic calcium concentrations ([Ca2+]c), which are critical for calcium-dependent signaling cascades.
  • Endothelial nitric oxide synthase (eNOS) activation is a key process in vascular function, regulated by intracellular calcium levels.

Purpose of the Study:

  • To investigate the role of p32 in regulating intracellular calcium ([Ca2+]) and its association with calcium-dependent eNOS activation in endothelial cells.
  • To evaluate the impact of p32 overexpression on endothelial function, nitric oxide (NO) production, and reactive oxygen species (ROS) generation.

Main Methods:

  • Adenovirus and plasmid-mediated p32 overexpression systems were employed.
  • Electron and confocal microscopy were used to determine p32 localization.
  • Vascular tension assays and biochemical analyses (Western blotting, NO/ROS measurements) were performed in vitro and in vivo models.

Main Results:

  • p32 overexpression localized to mitochondria and endoplasmic reticulum, increasing organelle [Ca2+] and decreasing cytosolic [Ca2+]c.
  • Decreased cytosolic [Ca2+]c attenuated the calcium/calmodulin dependent protein kinase II (CaMKII)/AKT/eNOS phosphorylation signaling cascade.
  • Increased p32 levels reduced NO production, augmented ROS generation, impaired vasorelaxation, and enhanced vasoconstriction.
  • Downregulation of arginase II (ArgII) was associated with p32 downregulation and contributed to CaMKII-dependent eNOS phosphorylation.

Conclusions:

  • Increased p32 protein levels induce endothelial dysfunction by attenuating the Ca2+-dependent signaling cascade.
  • Arginase II (ArgII) plays a role in the stability of p32 protein.
  • p32 represents a potential therapeutic target for vascular diseases linked to endothelial dysfunction.
Keywords:
p32calcium concentrationendoplasmic reticulummitochondriaendothelial nitric oxide synthase

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