PKC-β modulates Ca²⁺ mobilization through Stim1 phosphorylation.

Area of Science:

• Cellular Biology
• Molecular Biology
• Biochemistry

Background:

• Calcium ions are critical for cellular processes like proliferation and migration.
• Store-operated calcium entry (SOCE) regulates intracellular calcium levels, involving Orai1 and stromal interaction molecule 1 (Stim1).
• Protein kinases like ERK, PKA, and PAK modulate Stim1 activity, but PKC's role is unknown.

Purpose of the Study:

• To investigate if Protein Kinase C-beta (PKC-β) influences intracellular calcium dynamics via Stim1.
• To elucidate the interaction and phosphorylation of Stim1 by PKC-β.

Main Methods:

• Immune-precipitation and site-directed mutagenesis to study PKC-Stim1 interaction and phosphorylation.
• In vitro kinase assays to confirm direct phosphorylation.
• Confocal microscopy to observe intracellular calcium mobilization and SOCE activity.

Main Results:

• PKC directly interacts with and phosphorylates Stim1 in vitro.
• Stim1 phosphorylation at the C-terminus is crucial for regulating SOCE in HEK293 and HeLa cells.
• PKC activators inhibited SOCE, while PKC inhibitors activated it.

Conclusions:

• PKC-β plays a repressive role in regulating calcium entry through the Stim1-mediated SOCE channel.
• This study identifies a novel inhibitory mechanism of calcium signaling by PKC-β.