Criticality of the Phosphate Carrier SLC25A3 for Mitochondrial Inorganic Phosphate Uptake to Sustain Striated Muscle Function
Abstract
This project investigates the criticality of the mitochondrial phosphate carrier (PiC) for oxidative phosphorylation (oxphos; Aim 1) and buffering of mitochondrial matrix Ca2 (Aim 2). Aim 3 focuses on the generation of TAT fusion proteins for the PiC and their ability to rescue phenotypes induced by PiC depletion. In this reporting period (Nov 2019 Oct 2020), substantial progress was made on Aims 2 and 3. For Aim 2, we have almost completed a manuscript that investigates the role of the PiC in mitochondrial Ca2+ handling and the implications on cytosolic Ca2+ signaling in muscle fibers and force generation of intact muscle. These studies utilized a new mouse model in which PiC is deleted specifically in skeletal muscle (skm), in a Tamoxifen-inducible fashion. For the experiments, PiC was deleted by injecting 9-week old mice with Tamoxifen; skm mitochondria, intact fibers and whole muscle were harvested 2 weeks later at which point PiC protein was only tilde3 percent of normal levels. The main findings are summarized as follows. 1) Even very low PiC levels were sufficient to maintain normal mitochondrial Ca2+ uptake. 2) A larger PiC capacity then was needed to support normal mitochondrial Ca2+ uptake was needed to provide sufficient Pi to the mitochondrial matrix to bind to Ca2+ to an extent that occurs normally, indicating that PiC has greater control over matrix Ca2+ buffering than over mitochondrial Ca2+ uptake. 3) The higher matrix free Ca2+ observed in PiC-depleted skm mitochondria allowed for greater Ca2+ -induced stimulation of oxidative phosphorylation, suggesting that Pi buffering of matrix Ca2+ can serve to limit the Ca2+ available to stimulate oxidative phosphorylation. 4) Intact skm fibers and whole muscle were challenged with different stimulation protocols; PiC depletion substantially limited the rise in cytosolic Ca2+ and the time-to-peak of force generation in response to tetanic stimulation.
Document Details
- Document Type
- Technical Report
- Publication Date
- Oct 01, 2020
- Accession Number
- AD1123330
Entities
People
- Erin L Seifert
Organizations
- Thomas Jefferson University