Nuclear pores collapse in response to CO2 imaged with atomic force microscopy

Area of Science:

• Cell Biology
• Biophysics
• Molecular Biology

Background:

• Nuclear pore complexes (NPCs) regulate macromolecule transport between the nucleus and cytoplasm, controlling gene expression.
• NPC conformation dictates cargo movement and is influenced by factors like ATP and calcium.
• Previous research indicates ATP and calcium induce NPC contraction (increased height, decreased diameter).

Purpose of the Study:

• To investigate the effect of carbon dioxide (CO2) on the structural conformation of nuclear pore complexes (NPCs).
• To compare the CO2-induced NPC shape change with responses to ATP and calcium.
• To understand the potential functional implications of CO2-mediated NPC structural alterations.

Main Methods:

• Experiments utilized isolated nuclear envelopes from Xenopus laevis oocytes.
• Atomic force microscopy (AFM) was employed to image the cytoplasmic surface of NPCs on a glass substrate.
• The preparation was exposed to a 5% CO2 (95% O2) atmosphere at room temperature in a saturated O2 environment.

Main Results:

• Exposure to 5% CO2 induced a rapid and significant change in NPC structure.
• NPCs exhibited a decrease in both height and diameter, indicating pore closure.
• The central channel openings of NPCs virtually disappeared, and the structures appeared flattened.
• The observed CO2-induced NPC shape change was only slowly reversible.

Conclusions:

• Carbon dioxide (CO2) triggers a distinct NPC structural collapse, differing from ATP/calcium-induced changes.
• The observed pore closure suggests a potential mechanism for the functional isolation of the cell nucleus.
• NPCs demonstrate a sensitivity to CO2, impacting nuclear transport and potentially cellular function.