Novel role of phospholipase C-delta1: regulation of liver mitochondrial Ca2+ uptake.

Knox CD, Belous AE, Pierce JM, Wakata A, Nicoud IB, Anderson CD, Pinson CW, Chari RS
Am J Physiol Gastrointest Liver Physiol. 2004 287 (3): G533-40

PMID: 15107298 · DOI:10.1152/ajpgi.00050.2004

Mitochondrial Ca2+ (mCa2+) handling is an important regulator of liver cell function that controls events ranging from cellular respiration and signal transduction to apoptosis. Cytosolic Ca2+ enters mitochondria through the ruthenium red-sensitive mCa2+ uniporter, but the mechanisms governing uniporter activity are unknown. Activation of many Ca2+ channels in the cell membrane requires PLC. This activation commonly occurs through phosphitidylinositol-4,5-biphosphate (PIP2) hydrolysis and the production of the second messengers inositol 1,4,5-trisphosphate [I(1,4,5)P3] and 1,2-diacylglycerol (DAG). PIP2 was recently identified in mitochondria. We hypothesized that PLC exists in liver mitochondria and regulates mCa2+ uptake through the uniporter. Western blot analysis with anti-PLC antibodies demonstrated the presence of PLC-delta1 in pure preparations of mitochondrial membranes isolated from rat liver. In addition, the selective PLC inhibitor U-73122 dose-dependently blocked mCa2+ uptake when whole mitochondria were incubated at 37 degrees C with 45Ca2+. Increasing extra mCa2+ concentration significantly stimulated mCa2+ uptake, and U-73122 inhibited this effect. Spermine, a uniporter agonist, significantly increased mCa2+ uptake, whereas U-73122 dose-dependently blocked this effect. The inactive analog of U-73122, U-73343, did not affect mCa2+ uptake in any experimental condition. Membrane-permeable I(1,4,5)P3 receptor antagonists 2-aminoethoxydiphenylborate and xestospongin C also inhibited mCa2+ uptake. Although extra mitochondrial I(1,4,5)P3 had no effect on mCa2+ uptake, membrane-permeable DAG analogs 1-oleoyl-2-acetyl-sn-glycerol and DAG-lactone, which inhibit PLC activity, dose-dependently inhibited mCa2+ uptake. These data indicate that PLC-delta1 exists in liver mitochondria and is involved in regulating mCa2+ uptake through the uniporter.

MeSH Terms (24)

Adenosine Animals Blotting, Western Calcium Calcium-Binding Proteins Calcium Channel Agonists Calcium Channels Cell Membrane Estrenes Fluorescent Dyes Inositol 1,4,5-Trisphosphate In Vitro Techniques Isoenzymes Male Microscopy, Fluorescence Mitochondria, Liver Phosphodiesterase Inhibitors Phospholipase C delta Pyrrolidinones Rats Rats, Sprague-Dawley Spermine Stimulation, Chemical Type C Phospholipases

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