Nucleolin in the cell membrane promotes Ang II-mediated VSMC phenotypic switching by regulating the AT1R...

Area of Science:

• Cardiovascular Biology
• Cellular Signaling
• Molecular Mechanisms

Background:

• Nucleolin (NCL) is a key regulator in angiotensin II (Ang II)-induced vascular smooth muscle cell (VSMC) phenotypic switching.
• Understanding the precise regulatory mechanisms of NCL in this process is crucial for cardiovascular research.

Purpose of the Study:

• To elucidate the regulatory mechanisms by which Nucleolin (NCL) influences angiotensin II (Ang II)-induced phenotypic switching in vascular smooth muscle cells (VSMCs).
• To investigate the role of the Ang II type 1 receptor (AT1R) and associated signaling pathways (PKC/MAPK) in NCL-mediated VSMC responses.

Main Methods:

• Investigated Ang II effects on NCL expression and VSMC phenotypic switching.
• Analyzed NCL translocation, binding to AT1R, and the impact of NCL's GAR region.
• Utilized peptide-N-glycosidase F (PNGase F) to assess N-glycosylation's role.
• Examined NCL's influence on AT1R internalization, phosphorylation, and recycling pathways (Rab4, Rab11).
• Conducted in vivo experiments involving NCL knockdown to assess effects on blood pressure and vasculopathy.

Main Results:

• Ang II upregulated NCL expression and activated the PKC/MAPK pathway, inducing VSMC phenotypic switching.
• NCL translocated to the cell membrane and bound to AT1R, with the GAR region being critical for this interaction.
• Inhibition of NCL N-glycosylation by PNGase F suppressed VSMC phenotypic switching.
• NCL overexpression delayed Ang II-induced AT1R internalization by inhibiting phosphorylation and promoting recycling, while NCL knockdown had opposite effects.
• Knockdown of NCL in vivo reduced Ang II-induced hypertension and vasculopathy.

Conclusions:

• Nucleolin (NCL) plays a significant role in promoting Ang II-mediated VSMC phenotypic switching.
• NCL regulates AT1R internalization, a key mechanism through which it exerts its effects.
• These findings highlight NCL as a potential therapeutic target for cardiovascular diseases driven by Ang II signaling.