Expression of zinc transporters during the differentiation of erythroblasts from phenylhydrazine (PHZ)‐treated mice

Abstract

Zinc is required for the functions of several proteins related to erythroid differentiation. Excessive intracellular free Zn2+ interferes with incorporation of Fe2+ during heme biosynthesis. Therefore, intracellular zinc homeostasis during erythroid differentiation must be tightly regulated. To examine the suggested hypothesis, we prepared erythroblasts from spleens of PHZ-treated, anemic mice, of which further differentiation was induced by in vitro erythropoietin (EPO)-treatment. Based on QRT-PCR results, Zip8 and ZnT1 expression showed the highest responsiveness to EPO among the ten zinc transporters tested. Zip8 mRNA expression was highest prior to the time-point when erythroid δ-aminolevulinic acid synthase mRNA reached its maximal level (i.e., 24 h after EPO-treatment), while the ZnT1 mRNA expression level peaked afterwards. Furthermore, western blots of ZnT1 with differentiating PHZ-splenocytes and erythrocyte ghost cells revealed a similar trend in protein expression. These results suggest that Zip8 and ZnT1 could be the zinc transporters most directly involved in the regulation of zinc homeostasis during terminal erythroid differentiation. Specifically, Zip8 may facilitate the zinc uptake required for normal erythroid differentiation, while ZnT1 removes excessive free Zn2+ that may compete with Fe2+ during heme biosynthesis. Supported by NIH Grant DK 31127 and Boston Family Endowment funds.