Fatty acid-mediated calcium sequestration within intracellular calcium pools

Area of Science:

• Cellular Biology
• Biochemistry
• Physiology

Background:

• Intracellular calcium (Ca2+) pools are crucial for signaling.
• Endoplasmic reticulum (ER) heterogeneity influences Ca2+ pool dynamics.
• Ca2+ translocation between ER subcompartments involves GTP-activated mechanisms.

Purpose of the Study:

• To investigate the role of fatty acids in modulating intracellular Ca2+ pools.
• To characterize the specificity and mechanism of fatty acid-induced Ca2+ sequestration.
• To determine the release properties of Ca2+ sequestered by fatty acids.

Main Methods:

• Utilized GTP and various fatty acids (palmitate, pentadecanoate, etc.) to induce Ca2+ accumulation in ER pools.
• Employed palmitoyl-CoA to block the GTP-activated mechanism.
• Used 4,4'-diisothiocyanostilbene-2,2'-disulfonic acid to inhibit anion transport.
• Assessed Ca2+ release using ionophore A23187 and inositol 1,4,5-trisphosphate (InsP3).

Main Results:

• Palmitate (≥10 μM) and GTP induced substantial Ca2+ accumulation in a specific pool.
• Ca2+ accumulation was highly specific to fatty acid chain length (C15, C16 effective; others ineffective) and required saturation.
• Palmitate-induced Ca2+ sequestration was blocked by palmitoyl-CoA and inhibited by 4,4'-diisothiocyanostilbene-2,2'-disulfonic acid.
• Fatty acid-sequestered Ca2+ was readily released by A23187 but resistant to InsP3, unlike oxalate-sequestered Ca2+.

Conclusions:

• Fatty acids are specifically transported into ER lumen, mediating Ca2+ sequestration in a distinct substate.
• This fatty acid-mediated Ca2+ pool is GTP-dependent and chain-length specific.
• The sequestered Ca2+ is not readily released by InsP3, suggesting a novel regulatory mechanism.