College of Agriculture & Natural Resources
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The collections in this community comprise faculty research works, as well as graduate theses and dissertations.
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Item COORDINATED TRAFFICKING OF HEME TRANSPORTERS BY CARGO SORTING COMPLEXES IS ESSENTIAL FOR ORGANISMAL HEME HOMEOSTASIS(2025) Dutt, Sohini; Hamza, Iqbal IH; Animal Sciences; Digital Repository at the University of Maryland; University of Maryland (College Park, Md.)Heme, an iron-containing organic ring, is a vital cofactor responsible for diverse biologicalfunctions and is the major source of bioavailable iron in the human diet. As a hydrophobic and cytotoxic cofactor, heme must be transported in a highly controlled manner through membranes via specific intra- and inter-cellular pathways. However, the genes and pathways responsible for heme trafficking remain poorly understood. Unlike other metazoans, Caenorhabditis elegans cannot synthesize heme but requires heme for sustenance. Thus, C. elegans is an ideal animal model to identify heme trafficking pathways as it permits organismal heme homeostasis to be directly manipulated by controlling environmental heme. Heme is imported apically into the intestine by HRG-1-related permeases and exported basolaterally by MRP-5/ABCC5 to extra- intestinal tissues. Loss of mrp-5 causes embryonic lethality that can be suppressed by dietary heme supplementation raising the possibility that MRP-5-independent heme export pathways must exist. Here we show, by performing a forward genetic screen in mrp-5 null mutants, that loss of the vesicular cargo sorting Adaptor Protein complexes (AP-3) fully rescues mrp-5 lethality and restores heme homeostasis. Remarkably, intestinal heme accumulation due to mrp-5-deficiency causes a concomitant deficit in the lysosomal heme importer HRG-1 abundance and localization. Loss of both MRP-5 and AP-3 subunits resurrects HRG-1 levels and localization, thus underscoring the crucial role of HRG-1 in dictating mrp-5 mutant phenotypes. In the absence of MRP-5, heme is exported by SLC49A3 homolog, a previously uncharacterized transporter. Live- cell imaging reveals vesicular coalescence that facilitates heme transfer between the importers and exporters at the interface of lysosomal-related organelle. These results define a mechanistic model for metazoan heme trafficking and identifies SLC49A3 as a promising candidate for heme export in mammals.Item Investigating Copper Acquisition And Delivery via Transporters and a Pharmacological Chaperone in Copper-Deficient Worms and Mice(2019) Yuan, Sai; Kim, Byung-Eun; Animal Sciences; Digital Repository at the University of Maryland; University of Maryland (College Park, Md.)Copper (Cu) is a key micronutrient required for a variety of essential biochemical pathways. Systemic or tissue-specific Cu-deficiencies, caused by insufficient dietary Cu uptake or mutations in Cu transporting genes, result in impaired growth, neuropathy, ataxia, hypopigmentation, osteoporosis and anemia-like symptoms in mammals. How organisms regulate Cu homeostasis at the systemic levels in response to Cu deficiencies remain elusive. In this study, we use Caenorhabditis elegans (C. elegans), a genetically tractable, multi-tissue metazoan to explore Cu homeostasis and investigate these unknowns. The high-affinity Cu transporters encoded by CTR family genes are required for dietary Cu uptake and maintaining systemic Cu balance from yeast to mammals. However, little is known about Cu acquisition mechanisms in C. elegans. We identified ten CTR ortholog genes in C. elegans; of these, chca-1 was functionally characterized. Cu availability regulates transcription of chca-1 in both the intestine and hypodermis, and chca-1 is essential for normal growth, and reproduction in the worm. Additionally, altered Cu balance caused by the loss of CHCA-1 results in defects in Cu-responsive avoidance behavior. Identification of this CTR-like gene in C. elegans, which appears to be essential for normal Cu homeostasis in the worm, illustrates the importance of Cu delivery via CHCA-1 for normal metazoan development and behavioral phenotypes. In addition, we show that a Cu-binding pharmacological chaperone, elesclomol (ES), fully restores the developmental defects and Cu deficiencies in chca-1-depleted worms, as well as the lethality in worms lacking cua-1 expression (Cu exporter ATP7A ortholog), suggesting ES is able to efficiently deliver Cu from dietary sources to peripheral tissues through the intestine in C. elegans. Our study was further expanded to mammalian models such as cardiac-specific Ctr1-depleted (Ctr1hrt/hrt) mice. We found that ES administration fully restores the postnatal lethality, developmental defects and cardiac hypertrophy found in Ctr1hrt/hrt mice, as well as rescuing the secondary systemic Cu homeostasis responses, including aberrant ATP7A protein levels in the liver and intestine. Moreover, ES shows the potential ability to transport Cu across the blood-brain-barrier in in vitro studies. These results illustrate the capability of ES to rescue systemic Cu deficiency in worms and mice, independent of the presence of functional Cu transporters, and shed light on the therapeutic usage of ES in Cu-deficient human diseases.Item Genetic Characterization of Toxic Resistant Mutants in C. elegans(2010) Walston, Jonathan Dean; Hamza, Iqbal; Animal Sciences; Digital Repository at the University of Maryland; University of Maryland (College Park, Md.)Heme is an essential cofactor that plays a key role in diverse biological processes. Free heme, however, is hydrophobic and toxic to cellular macromolecules. C. elegans lack the heme biosynthetic pathway, and therefore contains a highly regulated trafficking network to redistribute heme throughout the worm. A forward genetic screen in C. elegans identified thirteen mutants which grow at toxic concentrations of heme in axenic liquid media. These mutants, termed them for Toxic HEMe resistant, belong to five complementation groups of which IQ7280, IQ7310, IQ8280 and IQ9110 strains were characterized. them mutants exhibit abnormal responses to heme analogs, mating defects, and growth on heme-deficient bacteria. Pyrosequencing analysis mapped IQ7310, IQ8280, and IQ7280 to a common genetic interval on chromosome I and IQ9110 to chromosome V. Solexa deep sequencing identified mutations in novel genes which may play an essential role in organismal heme homeostasis.