A new function for CD38/ADP-ribosyl cyclase in nuclear Ca2+ homeostasis

Area of Science:

• Cell Biology
• Molecular Biology
• Biochemistry

Background:

• Nucleoplasmic calcium ions (Ca2+) are crucial regulators of essential nuclear functions, including gene transcription and DNA repair.
• The precise mechanisms governing nuclear Ca2+ homeostasis are not fully understood, despite the presence of Ca2+ channels like inositol trisphosphate and ryanodine receptors in the nuclear membrane.

Purpose of the Study:

• To investigate the role of CD38/ADP-ribosyl cyclase in regulating nucleoplasmic Ca2+ levels.
• To elucidate the mechanism by which this enzyme influences nuclear Ca2+ homeostasis.

Main Methods:

• Localization and functional characterization of CD38/ADP-ribosyl cyclase in the inner nuclear membrane.
• Investigation of the enzyme's catalytic activity within the nucleoplasm.
• Assessment of the downstream effects of the enzyme's product on nuclear Ca2+ release.

Main Results:

• A functionally active CD38/ADP-ribosyl cyclase was identified in the inner nuclear membrane with its catalytic site located in the nucleoplasm.
• The enzyme catalyzes the conversion of nicotinamide adenine dinucleotide to cyclic adenosine diphosphate ribose (cADPR) within the nucleus.
• The generated cADPR was found to activate ryanodine receptors in the inner nuclear membrane, leading to nucleoplasmic Ca2+ release.

Conclusions:

• CD38/ADP-ribosyl cyclase plays a significant role in nucleoplasmic Ca2+ regulation.
• The enzyme acts as a key mediator of Ca2+ signaling within the nucleus by activating ryanodine receptors.
• This finding provides new insights into the mechanisms controlling nuclear Ca2+ homeostasis and its impact on nuclear functions.