Nuclear proton dynamics and interactions with calcium signaling

Area of Science:

• Cell Biology
• Biochemistry
• Molecular Biology

Background:

• Gene expression is regulated by biochemical signals impacting the nucleus.
• Mechanisms controlling nuclear pH (pHnuc) and its role in gene expression are poorly understood.
• Protons have an inherent affinity for nucleic acids and nuclear proteins.

Purpose of the Study:

• To investigate nuclear pH dynamics and its regulation.
• To explore the relationship between nuclear pH and gene expression.
• To understand the role of cytoplasmic buffers in nuclear pH homeostasis.

Main Methods:

• Imaging nuclear pH dynamics using the DNA-binding dye Hoechst 33342.
• Assessing proton diffusion and buffering capacity in the nucleus and cytoplasm.
• Investigating the influence of nuclear calcium (Ca2+) signaling on nuclear pH in cardiac myocytes.

Main Results:

• Nuclear pH dynamics can be visualized using Hoechst 33342.
• Cytoplasmic mobile buffers are the primary source of nuclear pH buffering.
• Proton diffusion is faster in the nucleoplasm than in the cytoplasm.
• Nuclear pH is sensitive to nuclear Ca2+ signals, with altered Ca2+ release leading to nuclear alkalinization.

Conclusions:

• Cytoplasmic mobile buffers play a crucial role in maintaining nuclear pH homeostasis.
• A novel mechanism linking nuclear Ca2+ signaling to nuclear pH regulation via competitive binding to mobile buffers is proposed.
• This Ca2+-pH interaction may create a pH gradient sensitive to nuclear Ca2+ signaling, impacting cardiac nuclear biology.