Bachkoenig OA, Gottschalk B, Malli R, Graier WF. An unexpected effect of risperidone reveals a nonlinear relationship between cytosolic Ca
2+ and mitochondrial Ca
2+ uptake.
Curr Top Membr 2022;
90:13-35. [PMID:
36368872 DOI:
10.1016/bs.ctm.2022.09.001]
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Abstract
Mitochondria actively contribute to cellular Ca2+ homeostasis. The molecular mechanisms of mitochondrial Ca2+ uptake and release are well characterized and are attributed to the multi-protein assembly of the mitochondrial Ca2+ uniporter complex (MCUC) and the mitochondrial sodium-calcium exchanger (NCLX), respectively. Hence, Ca2+ transfer from the endoplasmic reticulum (ER) and store-operated Ca2+ entry (SOCE) into the mitochondrial matrix has been quantitatively visualized on the subcellular level using targeted fluorescent biosensors. However, a correlation between the amplitude of cytosolic Ca2+ elevation with that in the mitochondrial matrix has not been investigated in detail so far. In the present study, we combined the Ca2+-mobilizing agonist histamine with the H1-receptor antagonist risperidone to establish a well-tunable experimental approach allowing the correlation between low, slow, high, and fast cytosolic and mitochondrial Ca2+ signals in response to inositol 1,4,5-trisphosphate (IP3)-triggered ER Ca2+ release. Our present data confirm a defined threshold in cytosolic Ca2+, which is necessary for the activation of mitochondrial Ca2+ uptake. Moreover, our data support the hypothesis of different modes of mitochondrial Ca2+ uptake depending on the source of the ion (i.e., ER vs SOCE).
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