Stimulation of the human mitochondrial transporter ABCB10 by zinc-mesoporphrin

Abstract

Heme biosynthesis occurs through a series of reactions that take place within the cytoplasm and mitochondria, so intermediates need to move across these cellular compartments. However, the specific membrane transport mechanisms involved in the process are not yet identified. The ATP-binding cassette protein ABCB10 is essential for normal heme production, as knocking down this transporter in mice is embryonically lethal and accompanied by severe anemia plus oxidative damage. The role of ABCB10 is unknown, but given its location in the inner mitochondrial membrane, it has been proposed as a candidate to export either an early heme precursor or heme. Alternatively, ABCB10 might transport a molecule important for protection against oxidative damage. To help discern between these possibilities, we decided to study the effect of heme analogs, precursors, and antioxidant peptides on purified human ABCB10. Since substrate binding increases the ATP hydrolysis rate of ABC transporters, we have determined the ability of these molecules to activate purified ABCB10 reconstituted in lipid nanodiscs using ATPase measurements. Under our experimental conditions, we found that the only heme analog increasing ABCB10 ATPase activity was Zinc-mesoporphyrin. This activation of almost seventy percent was specific for ABCB10, as the ATPase activity of a negative control bacterial ABC transporter was not affected. The activation was also observed in cysteine-less ABCB10, suggesting that Zinc-mesoporphyrin’s effect did not require binding to typical heme regulatory motifs. Furthermore, our data indicate that ABCB10 was not directly activated by neither the early heme precursor delta-aminolevulinic acid nor glutathione, downsizing their relevance as putative substrates for this transporter. Although additional studies are needed to determine the physiological substrate of ABCB10, our findings reveal Zinc-mesoporphyrin as the first tool compound to directly modulate ABCB10 activity and raise the possibility that some actions of Zinc-mesoporphyrin in cellular and animal studies could be mediated by ABCB10.

Genomic adaptation of Ethiopian indigenous cattle to high altitude

“…Last but not least, among the genes present within candidate genomic regions detected by both XP-CLR and iHS analyses, we do have ABCB10 (Table 3). This gene was previously reported in candidate selected regions in humans, and several other species, including cattle (Bayeva et al, 2013;Martinez et al, 2020). Its function is related to iron metabolism and heme biosynthesis (Haase, 2010;Shah et al, 2013;Yamamoto et al, 2014;Seguin and Ward, 2018).…”

Knockout Mouse Studies Show Mitochondrial CLPP Peptidase and CLPX Unfoldase to Act in Matrix Condensates Near IMM, as Fast Stress Response in Protein Assemblies for Transcript Processing, Translation, and Heme Production

“…Firstly, MFRN1 (also known as SLC25A37 or mitoferrin-1), which imports iron into the mitochondrial matrix [155], secondly ABCB10, which exports biliverdin to the cytosol [156], and thirdly ABCB7, which exports glutathione-coordinated iron-sulfur clusters to the cytosol [157] are connected to the IMM-associated heme biosynthesis complex according to several consistent reports. There is still debate [147] whether the tight association of IMM transmembrane proteins with this metabolon goes beyond the biliverdin / zinc-mesoporphyrin transporter ABCB10 [158][159][160] to include also the TMEM14C protoporphyrin-IX transporter [161][162][163][164], the protoporphyrin-IX transport modulator ANT2 [165] and the glutathione/succinate transport modulator OGC [166,167]. Enzyme complexes with similar isolation of reaction intermediates from the surrounding matrix have been observed also e.g.…”

Knockout Mouse Studies Show That Mitochondrial CLPP Peptidase and CLPX Unfoldase Act in Matrix Condensates near IMM, as Fast Stress Response in Protein Assemblies for Transcript Processing, Translation, and Heme Production

“…Firstly, MFRN1 (also known as SLC25A37 or mitoferrin-1), which imports iron into the mitochondrial matrix [ 155 ]; secondly, ABCB10, which exports biliverdin to the cytosol [ 156 ]; and thirdly, ABCB7, which exports glutathione-coordinated iron–sulfur clusters to the cytosol [ 157 ], are connected to the IMM-associated heme biosynthesis complex, according to several consistent reports. There is still debate [ 147 ] about whether the tight association of IMM transmembrane proteins with this metabolon goes beyond the biliverdin/zinc-mesoporphyrin transporter ABCB10 [ 158 , 159 , 160 ] to include also the TMEM14C protoporphyrin-IX transporter [ 161 , 162 , 163 , 164 ], the protoporphyrin-IX transport modulator ANT2 [ 165 ], and the glutathione/succinate transport modulator OGC [ 166 , 167 ]. Enzyme complexes with similar isolations of reaction intermediates from the surrounding matrix have also been observed, e.g., during L-arginine metabolism and bacterial cobalamin metabolism [ 168 , 169 ].…”