Metal intracellular partitioning as a detoxification mechanism for mummichogs (Fundulus heteroclitus) living in metal-polluted salt marshes

Abstract

Intracellular partitioning of trace metals is critical to metal detoxification in aquatic organisms. In the present study, we assessed metal (Cd, Cu, Pb, and Zn) handling capacities of mummichogs (Fundulus heteroclitus) in metal-polluted salt marshes in New York, USA by examining metal intracellular partitioning. Despite the lack of differences in the whole body burdens, partitioning patterns of metals in intracellular components (heat-stable proteins, heat-denaturable proteins, organelles, and metal-rich granules) revealed clear differential metal handling capacities among the populations of mummichogs. In general, mummichogs living in metal-polluted sites stored a large amount of metals in detoxifying cellular components, particularly metal-rich granules (MRG). Moreover, only metals associated with MRG were consistently correlated with variations in the whole body burdens. These findings suggest that metal detoxification through intracellular partitioning, particularly the sequestration to MRG, may have important implications for metal tolerance of mummichogs living in chronically metal-polluted habitats.

Subcellular partitioning profiles and metallothionein levels in indigenous clams Moerella iridescens from a metal-impacted coastal bay

“…S5), suggesting that the "spillover" model is not adequate to represent Cd-handling for M. iridescens when chronically exposed in the field and that Cd detoxification is incomplete as indicated by the presence of Cd in these "inappropriate" fractions. Other researchers have observed similar intracellular partitioning patterns of Cd for relevant organisms (Giguère et al, 2006;Voets et al, 2009;Goto and Wallace, 2010;Rosabal et al, 2015). Notably, the increase in Cd concentrations in HDP fractions seemed to occur early in the bioaccumulation gradients up to a total tissue concentration of approximate 4.5 nmol Cd g −1 dw, and then not show any further increase (Fig.…”

“…S5), suggest that Cd detoxification occurred mainly by MT and MT-like proteins. In contrast to some aquatic organisms in which Cd tends to be mainly sequestrated in the MRG fraction (Goto and Wallace, 2010), M. iridescens preferentially reduces the availability of the non-essential metal Cd by binding it to the HSP fraction. Other researchers have observed the predominance of the HSP fraction in detoxifying Cd in invertebrates exposed to Cd in the laboratory (Dubois and Hare, 2009;Xie and Buchwalter, 2011) and in field-collected organisms (Giguère et al, 2006;Oyoo-Okoth et al, 2012), suggesting their similar metalhandling strategies to cope with incoming Cd.…”

Subcellular distribution of Cd and Zn and MT mRNA expression in the hepatopancreas of Sinopotamon henanense after single and co-exposure to Cd and Zn

“…In principle, the mitochondrial compartment should be metal-sensitive (Silverberg, 1976), and the increasing metal concentration would suggest that metal detoxification was incomplete. A similar evidence of "spillover" of non-essential metals onto metal sensitive sites has also been reported for other aquatic organisms living along metal exposure gradients (Cain et al, 2004;Campbell and Hare, 2009;Voets et al, 2009;Goto and Wallace, 2010;Wang et al, 2011). Although some extent of Cd accumulation increase was seen in the Mic & Lys and cellular debris & nuclei fractions, it is really difficult to interpret their role and predict the toxicity of Cd.…”

Global Transcriptome Profiling Reveals Molecular Mechanisms of Metal Tolerance in a Chronically Exposed Wild Population of Brown Trout

“…28 MT-bound metals contribute to the metabolically detoxified cellular fraction and can also be stored in metal rich granules for even more stable, long-term storage. 31 Increased MT synthesis has been extensively shown to occur in response to many metals, in both short-term laboratory exposures and in chronically exposed wild fish and it is the most consistent and sometimes only, mechanism of metal tolerance in fish [e.g., refs (14, 15 and 32−34)]. A single MT isoform is predominantly induced by metals in fish; free metal ions bind mtf1 transcription factors, which then bind metal response elements (MREs) in its promoter region, stimulating transcription.…”