Phospholipase C-η2 is activated by elevated intracellular Ca(2+) levels

Area of Science:

• Biochemistry
• Cell Biology
• Molecular Pharmacology

Background:

• Phospholipase C-η2 (PLCη2) is a novel enzyme with uncharacterized cellular activity.
• Understanding PLCη2 function is crucial for elucidating cellular signaling pathways.

Purpose of the Study:

• To characterize the activity and regulation of Phospholipase C-η2 (PLCη2).
• To investigate the role of PLCη2 domains in enzyme activity and localization.
• To explore PLCη2's potential contribution to calcium signaling.

Main Methods:

• Assessing PLCη2 activity via [(3)H]inositol phosphate release in transfected COS7 cells.
• Utilizing monensin to stimulate PLCη2 activity and CGP-37157 to investigate mitochondrial involvement.
• Employing site-directed mutagenesis to probe the function of PH and C2 domains.

Main Results:

• PLCη2 activity was significantly increased by monensin, indicating a role for Na(+)/Ca(2+)-exchange.
• Direct activation of PLCη2 by extracellular calcium (<1µM) was confirmed.
• A PH domain mutant showed no activity due to impaired membrane association.
• C2 domain mutations, particularly at D920, affected activity and highlighted its regulatory role, but not Ca(2+) sensitivity.

Conclusions:

• PLCη2 is a novel calcium-sensitive enzyme.
• Membrane association via the PH domain is essential for PLCη2 activity.
• The C2 domain plays a regulatory role in PLCη2 activity, but not calcium activation.
• PLCη2 likely amplifies intracellular calcium transients and mediates crosstalk between calcium compartments.