Physiology and Biophysics, Department of Biological Sciences and Pathobiology, University of Veterinary Medicine, Vienna, Austria.
Acta Physiol (Oxf). 2024 Jun;240(6):e14143. doi: 10.1111/apha.14143. Epub 2024 Apr 5.
Metabolic reprogramming in cancer cells has been linked to mitochondrial dysfunction. The mitochondrial 2-oxoglutarate/malate carrier (OGC) has been suggested as a potential target for preventing cancer progression. Although OGC is involved in the malate/aspartate shuttle, its exact role in cancer metabolism remains unclear. We aimed to investigate whether OGC may contribute to the alteration of mitochondrial inner membrane potential by transporting protons.
The expression of OGC in mouse tissues and cancer cells was investigated by PCR and Western blot analysis. The proton transport function of recombinant murine OGC was evaluated by measuring the membrane conductance (G) of planar lipid bilayers. OGC-mediated substrate transport was measured in proteoliposomes using C-malate.
OGC increases proton G only in the presence of natural (long-chain fatty acids, FA) or chemical (2,4-dinitrophenol) protonophores. The increase in OGC activity directly correlates with the increase in the number of unsaturated bonds of the FA. OGC substrates and inhibitors compete with FA for the same protein binding site. Arginine 90 was identified as a critical amino acid for the binding of FA, ATP, 2-oxoglutarate, and malate, which is a first step towards understanding the OGC-mediated proton transport mechanism.
OGC extends the family of mitochondrial transporters with dual function: (i) metabolite transport and (ii) proton transport facilitated in the presence of protonophores. Elucidating the contribution of OGC to uncoupling may be essential for the design of targeted drugs for the treatment of cancer and other metabolic diseases.
癌细胞中的代谢重编程与线粒体功能障碍有关。线粒体 2-氧戊二酸/苹果酸载体（OGC）已被认为是预防癌症进展的潜在靶点。尽管 OGC 参与了苹果酸/天冬氨酸穿梭，但它在癌症代谢中的确切作用仍不清楚。我们旨在研究 OGC 是否通过转运质子来参与改变线粒体内膜电位。
通过 PCR 和 Western blot 分析研究了 OGC 在小鼠组织和癌细胞中的表达。通过测量平面脂质双层的膜电导（G）来评估重组鼠 OGC 的质子转运功能。在含有 C-苹果酸的蛋白脂质体中测量 OGC 介导的底物转运。
OGC 仅在存在天然（长链脂肪酸，FA）或化学（2,4-二硝基苯酚）质子载体的情况下增加质子 G。OGC 活性的增加与 FA 的不饱和键数量的增加直接相关。OGC 的底物和抑制剂与 FA 竞争相同的蛋白结合位点。精氨酸 90 被确定为 FA、ATP、2-氧戊二酸和苹果酸结合的关键氨基酸，这是了解 OGC 介导的质子转运机制的第一步。
OGC 将具有双重功能的线粒体转运蛋白家族扩展为：（i）代谢物转运和（ii）在质子载体存在下促进质子转运。阐明 OGC 对解偶联的贡献对于设计用于治疗癌症和其他代谢疾病的靶向药物可能至关重要。
