Interhelical interactions within the STIM1 CC1 domain modulate CRAC channel activation

Area of Science:

• Molecular biology
• Cellular signaling
• Structural biology

Background:

• The calcium release-activated calcium channel is regulated by the endoplasmic reticulum calcium sensor STIM1.
• STIM1 activation involves a conformational change from a tight to an extended state, controlled by a coiled-coil clamp (CC1-CC3 domains).
• Mutations in STIM1, like R304W linked to Stormorken disease, can lead to altered activation.

Purpose of the Study:

• To elucidate the structural and functional role of interhelical interactions within the STIM1 CC1 domain.
• To understand how these interactions modulate the CC1-CC3 clamp and control STIM1 activation.
• To investigate the mechanism underlying the gain-of-function mutation STIM1 R304W.

Main Methods:

• Nuclear magnetic resonance (NMR) spectroscopy to determine the solution structure of the STIM1 CC1 domain.
• Site-directed mutagenesis to probe the function of specific interhelical sites within the CC1 domain.
• Analysis of STIM1 conformational changes and store-dependent activation behavior.

Main Results:

• The STIM1 CC1 domain adopts a three-helix bundle structure stabilized by interhelical contacts.
• These interhelical contacts are disrupted in the Stormorken disease mutant STIM1 R304W.
• Mutations at key interhelical sites in CC1 restore normal activation in the STIM1 R304W mutant.

Conclusions:

• Interhelical interactions within the STIM1 CC1 domain are critical for maintaining the coiled-coil clamp's integrity.
• Modulating these interactions affects the clamp strength and controls STIM1's store-dependent activation.
• This study provides insights into STIM1 regulation and the molecular basis of Stormorken disease.