TheHansenula polymorphaMitochondrial Carrier Family proteins Mir1 and Aac2 are dually localized at peroxisomes and mitochondria

Abstract

Peroxisomes are ubiquitous cell organelles involved in various metabolic pathways. In order to properly function, several cofactors, substrates and products of peroxisomal enzymes need to pass the organellar membrane. So far only a few transporter proteins have been identified. We analysed peroxisomal membrane fractions purified from the yeastHansenula polymorphaby untargeted label-free quantitation mass spectrometry. As expected, several known peroxisome-associated proteins were enriched in the peroxisomal membrane fraction. In addition, several other proteins were enriched, including mitochondrial transport proteins. Localization studies revealed that two of them, the mitochondrial carrier family proteins Aac2 and Mir1, have a dual localization on mitochondria and peroxisomes. To better understand the molecular mechanisms of dual sorting, we tested the localization of Mir1 in cells lacking Pex3 or Pex19, two peroxins that play a role in targeting of peroxisomal membrane proteins. In these cells Mir1 only localized to mitochondria, indicating that Pex3 and Pex19 are required to sort Mir1 to peroxisomes. Analysis of the localization of various truncated versions of Mir1 in wild-typeH. polymorphacells revealed that several localized to mitochondria, but only one, consisting of the transmembrane domains 3-6, was peroxisomal. Peroxisomal localization of this construct was lost in aMIR1deletion strain, indicating that full length Mir1 was required for the localization of the truncated protein to peroxisomes. Our data suggest that only full length Mir1 sorts to peroxisomes, while Mir1 contains multiple regions with mitochondrial sorting information.

Integrative Omics reveals changes in the cellular landscape of yeast without peroxisomes

“…We therefore wondered whether this could be related to dual localization on peroxisomes and mitochondria. This option was also inspired by recent reports on the dual localization of two other mitochondrial inner membrane carriers on peroxisomes and mitochondria S. cerevisiae Pet9, alias Aac2 (van Roermund et al, 2022) and H. polymorpha Mir1 (Pedersen et al, 2023 preprint ). Moreover, although a peroxisomal pyruvate transporter was predicted to exist, because of the presence of the pyruvate producing enzyme Str3 in the matrix, it was never identified.…”