Biology subjects

Piotrowski, M.

Publications and source records attributed to Piotrowski, M..

3 recordsLinked to original sources

bioRxiv2024

Metabolic mapping of the human solute carrier superfamily

Solute carrier (SLC) transporters govern most of the chemical exchange across cellular membranes and are integral to metabolic regulation, which in turn is linked to cellular function and identity. Despite their key role, individual functions of the members of the SLC superfamily were not evaluated systematically. We determined the metabolic and transcriptional profiles upon SLC overexpression in knock-out or wild-type isogenic cell backgrounds. Targeted metabolomics provided a fingerprint of 189 intracellular metabolites, while transcriptomics offered insights into cellular programs modulated by SLC expression. Beyond the metabolic profiles of 102 SLCs directly related to their known substrates, we also identified putative substrates or metabolic pathway connections for 71 SLCs without previously annotated bona fide substrates, including SLC45A4 as a new polyamine transporter. By comparing the molecular profiles, we identified functionally related SLC groups, including some with distinct impacts on osmolyte balancing and glycosylation. The assessment of functionally related human genes presented here may serve as a blueprint for other systematic studies of human gene function and supports future investigations into the functional roles of SLCs.

systems biology↗

bioRxiv2022

Arabidopsis Nicotianamine Synthases (NAS) comprise a common core-NAS domain fused to a variable auto-inhibitory C-terminus

Nicotianamine Synthase (NAS) catalyzes the biosynthesis of nicotianamine (NA) from the 2-aminobutyrate moieties of three S-adenosylmethionine molecules. NA has central roles in metal nutrition and metal homeostasis of flowering plants. Despite the availability of crystal structures of archaeal and bacterial NAS-like proteins that carry out simpler aminobutanoyltransferase reactions, the enzymatic function of NAS remains poorly understood. Here we report amino acids essential for the activity of AtNAS1 based on structural modeling and site-directed mutagenesis. An enzyme-coupled continuous activity assay allowed us to compare differing NAS proteins identified through multiple sequence alignments and phylogenetic analyses. In most class Ia and b NAS proteins of dicotyledonous and monocotyledonous angiosperm plants, respectively, the core-NAS domain is fused to a variable C-terminal domain. Compared to fungal and moss NAS (class III) that consist merely of the core-NAS domain, NA biosynthetic activities of the four paralogous Arabidopsis NAS proteins were far lower. Yet their C-terminally trimmed core-NAS variants exhibited strongly elevated activities. Out of 320 amino acids of AtNAS1, twelve, 287-TRGCMFMPCNCS-298, accounted for the auto-inhibitory effect of the C-terminus, with approximately one third contributed by N296 within a CNCS motif that is conserved in Arabidopsis. No detectable NA biosynthesis was mediated by two representatives of groups of plant NAS proteins that naturally lack the C-terminal domain, class Ia Arabidopsis halleri NAS5, and Medicago truncatula NAS2 of class II which is found in dicots and diverged early during the evolution of flowering plants. Our results suggest that NAS activity is under stringent post-translational control in plants.

plant biology↗

bioRxiv2021

Root-to-shoot iron partitioning in Arabidopsis requires IRON-REGULATED TRANSPORTER1 (IRT1)

IRON-REGULATED TRANSPORTER1 (IRT1) is the root high-affinity ferrous iron uptake system and indispensable for the completion of the life cycle of Arabidopsis thaliana without vigorous iron (Fe) supplementation. Here we provide evidence supporting a second role of IRT1 in root-to-shoot mobilization of Fe. We show that the irt1-2 (pam42) mutant over-accumulates Fe in roots, most prominently in the cortex of the differentiation zone, when compared to the wild type. Shoots of irt1-2 are severely Fe-deficient according to Fe content and marker transcripts, as expected. We generated irt1-2 lines producing IRT1 mutant variants carrying single amino-acid substitutions of key residues in transmembrane helices IV and V, Ser206 and His232, which are required for transport activity in yeast. In the transgenic Arabidopsis lines, short-term root Fe uptake rates and secondary substrate Mn accumulation resemble those of irt1-2, suggesting that these plants remain incapable of IRT1-mediated root Fe uptake. Yet, IRT1S206A partially complements rosette dwarfing and leaf chlorosis, as well as root-to-shoot Fe partitioning and gene expression defects of irt1-2, all of which are fully complemented by wild-type IRT1. Taken together, these results suggest a function for IRT1 in root-to-shoot Fe partitioning that does not require Fe transport activity of IRT1. Among the genes of which transcript levels are partially dependent on IRT1, we identify MYB DOMAIN PROTEIN10, MYB DOMAIN PROTEIN72 and NICOTIANAMINE SYNTHASE4 as candidates for effecting IRT1-dependent Fe mobilization in roots. Understanding the biological functions of IRT1 will help to improve iron nutrition and the nutritional quality of agricultural crops.

plant biology↗