Imaging the spatial dynamics of calmodulin activation during mitosis

Area of Science:

• Cell Biology
• Molecular Signaling

Background:

• Calcium ions are vital signaling molecules in most cell types.
• Calmodulin is a key calcium sensor regulating cell function via interactions with kinases and phosphatases.
• The spatiotemporal patterns of calmodulin activation within cells remain largely uncharacterized.

Purpose of the Study:

• To investigate the spatiotemporal patterns of calmodulin activation during mitosis in living cells.
• To determine the role of calmodulin activation in mitotic progression.
• To demonstrate the utility of novel fluorescent probes for studying protein activation.

Main Methods:

• Utilized a novel fluorescent calmodulin adduct (TA-calmodulin) to continuously monitor calmodulin activation in living cells.
• Observed calmodulin activation patterns during mitosis.
• Employed a high-affinity calmodulin-binding peptide to inhibit calmodulin function.

Main Results:

• Calmodulin activation was observed to be local and episodic within the nucleus and mitotic spindle during mitosis.
• The spatial and temporal patterns of calmodulin activation differed from calcium signals and were not predictable from calcium increases alone.
• Inhibition of calmodulin activation using a novel peptide blocked both entry into and exit from mitosis, demonstrating its essential role.

Conclusions:

• Calmodulin plays a critical regulatory role in mitotic transitions (entry and exit).
• Fluorescent calmodulin adducts are effective tools for studying protein activation in living cells with high temporal and spatial resolution.