Evaluating Calmodulin-Protein Interactions by Rapid Photoactivated Cross-Linking in Live Cells Metabolically Labeled...

Area of Science:

• Cellular Biology
• Biochemistry
• Molecular Biology

Background:

• Calcium ions (Ca²⁺) act as crucial second messengers in cellular signaling pathways.
• The calcium sensor protein calmodulin plays a central role in mediating cellular responses to calcium signals.
• Understanding calmodulin's interactions is key to deciphering calcium-mediated cellular processes.

Purpose of the Study:

• To identify proteins that interact with calmodulin under various cellular calcium conditions.
• To elucidate the role of calmodulin in shaping cellular responses to dynamic calcium signals.
• To discover novel calmodulin-interacting proteins with potential physiological significance.

Main Methods:

• Utilized rapid photoactivated cross-linking to capture calmodulin-interacting proteins in metabolically labeled cells.
• Employed affinity tagging of calmodulin and stringent enrichment of tagged adducts.
• Identified and quantified captured proteins using liquid chromatography-tandem mass spectrometry (LC-MS/MS).

Main Results:

• Identified a total of 489 proteins interacting with calmodulin, including 27 known interactors.
• Defined a high-specificity group of 170 proteins, of which ~60% showed altered capture with calcium manipulation.
• Discovered 29 high-specificity proteins whose capture decreased upon extracellular calcium removal, suggesting localization in calcium microdomains.

Conclusions:

• The study successfully identified a comprehensive set of calmodulin-interacting proteins, including potentially novel ones.
• Calcium manipulation significantly affects the interaction profile of high-specificity calmodulin-binding proteins.
• A subset of identified proteins likely resides in or near localized high-calcium microdomains, implicating them in specific calcium signaling events.