bims-mignad 2025-08-31 papers

Issue of 2025–08–31
two papers selected by
Melisa Emel Ermert, Amsterdam UMC

Neurochem Res. 2025 Aug 23. 50(5): 275

Coapplication of Adenine with Inosine or Guanosine Supports Rapid ATP Restoration by ATP-deprived Cultured Primary Astrocytes.

Gabriele Karger, Ralf Dringen.

Astrocytes contain a high concentration of adenosine triphosphate (ATP) that enables these cells to perform their physiological functions in brain. To investigate the mechanisms involved in astrocytic ATP restoration, the ATP content of cultured primary rat astrocytes was first depleted by a preincubation with the mitochondrial uncoupler BAM15 before extracellular substrates and their combinations were applied to foster ATP restoration. To test for the contribution of the purine salvage pathway to synthesize new adenosine monophosphate (AMP) for ATP restoration, several purine nucleosides and purine bases as well as their combinations were applied. In the absence of glucose, partial ATP restoration was found for incubations with inosine and guanosine that was lowered by forodesine, an inhibitor of purine nucleoside phosphorylase. In glucose-fed cells, the coapplication of micromolar concentrations of adenine with inosine or guanosine, but not with ribose, accelerated ATP restoration in a concentration-dependent manner. By such treatments, 80% of the initial ATP content were restored within 40 min. The supporting effects of inosine and guanosine on ATP restoration were prevented by the presence of forodesine, demonstrating the contribution of purine nucleoside phosphorylase in the ATP restoration observed. These data demonstrate that ATP-deprived astrocytes need for rapid ATP restoration - in addition to glucose as energy substrate - an adenine source and inosine or guanosine as precursor for the ribose phosphate moiety of ATP.

Keywords: ATP restoration; Astrocytes; Guanosine; Inosine; Purine nucleosides; Purine salvage pathway; Ribose

DOI: https://doi.org/10.1007/s11064-025-04511-x

EMBO J. 2025 Aug 26.

RTN4IP1 is required for the final stages of mitochondrial complex I assembly and CoQ biosynthesis.

Monika Oláhová, Rachel M Guerra, Jack J Collier, Juliana Heidler, Kyle Thompson, Chelsea R White, Paulina Castañeda-Tamez, Alfredo Cabrera-Orefice, Robert N Lightowlers, Zofia M A Chrzanowska-Lightowlers, Alexander Galkin, Ilka Wittig, David J Pagliarini, Robert W Taylor.

A biochemical deficiency of mitochondrial complex I (CI) underlies approximately 30% of cases of primary mitochondrial disease, yet the inventory of molecular machinery required for CI assembly remains incomplete. We previously characterised patients with isolated CI deficiency caused by segregating variants in RTN4IP1, a gene that encodes a mitochondrial NAD(P)H oxidoreductase. Here, we demonstrate that RTN4IP1 deficiency causes a CI assembly defect in both patient fibroblasts and knockout cells, and report that RTN4IP1 is a bona fide CI assembly factor. Complexome profiling revealed accumulation of unincorporated ND5-module and impaired N-module production. RTN4IP1 patient fibroblasts also exhibited defective coenzyme Q biosynthesis, substantiating a second function of RTN4IP1. Thus, our data reveal RTN4IP1 plays necessary and independent roles in both the terminal stages of CI assembly and in coenzyme Q metabolism, and that pathogenic RTN4IP1 variants impair both functions in patients with mitochondrial disease.

Keywords: Coenzyme Q; Complex I Assembly; Complexome Profiling; Mitochondria; RTN4IP1

DOI: https://doi.org/10.1038/s44318-025-00533-x