Stimulation by cadmium of myohemerythrin-like cells in the gut of the annelidNereis diversicolor

Abstract

Trace metals, whether essential such as Cu and Zn or nonessential such as Cd, are taken up by aquatic invertebrates from both food and solutions. After ingestion, the metal is transported around the body, perhaps to be accumulated in particular target organs or even to be excreted (Rainbow, 1998). In most invertebrates, body concentrations of the non-essential metal Cd do not appear to be regulated (Rainbow, 1985;Amiard et al., 1987;Rainbow, 1998). Metal toxicity is often postulated to arise from reactions occurring in the cytosol, through nonspecific binding of the metal to non-thionein ligands, which are physiologically important molecules (metalloenzymes or small peptides such as glutathione) and are inactivated by metal binding (Mason and Jenkins, 1995). Control of intracellular metal toxicity and detoxification of accumulated trace metals is generally achieved via the production of metal-binding ligands that sequester metals. These cellular ligands can be found in the particulate fraction of the cells such as mineral deposits, granules or lysosomes (George, 1990;Mason and Jenkins, 1995) and in the cytosol such as metallothioneins (Engel and Roesijadi, 1987). Metallothioneins, a family of low molecular mass cysteine-rich proteins, have been shown to occur in most zoological taxa (Amiard and Cosson, 1997). However, in polychaetous annelids this type of protein has not yet been isolated.Nereis diversicolor (Hediste diversicolor, recent denomination) is a polychaete living in the mud of estuaries which, in Europe, is routinely contaminated by heavy metals. Previous work (Nejmeddine et al., 1988) showed that in animals exposed to Cd the metal was bound to two pools of proteins of high molecular mass (metalloprotein I, MPI, >67·kDa) and low molecular mass (MPII, of about 20·kDa). MPI is the extracellular hemoglobin of this annelid (Demuynck and Dhainaut-Courtois, 1993). The primary structure of MPII isolated from whole worms was different from that of a metallothionein, consisting of 119 amino acid residues with only one cysteine residue , but shares 80.8% identity with the myohemerythrin isolated by Takagi and Cox (1991) from the same species. MPII is a Cd-binding protein but is not a metallothionein. Metallothioneins are known to be induced by essential (Cu or Zn) and non-essential (Cd) metals and are thought to be important both in the detoxification of trace metals and in the metabolism of intracellular Cu and Zn, as in the scavenging of reactive oxygen species (Palmiter, 1998;Klaassen et al., 1999). However, MPII appeared to correspond to a myohemerythrinlike pigment, known to play a mainly respiratory role and with no known function of detoxification. Immunocytochemical studies showed that MPII is located in granulocytes I Isolated guts of Nereis diversicolor revealed the existence of a cadmium-binding protein, the MPII, belonging to the group of hemerythrins and myohemerythrins. The presence of MPII in the cells of the intestine was demonstrated by immunocytochemistry, using anti-MPII, a monoclonal antibod...

Effect of Heavy Metals Pollution on Protein Biosynthesis in Catfish

“…These two metals were found to be responsible for different types of chromosomal aberrations and lower mitotic index in the fish [52]. Demuynck added that cadmium-binding protein level in the cells of intestine was increased after exposure to Cd, so it appears that this protein will be synthesized as a response to Cd over exposure [52]. Abdelhamid and El-Ayouty, [11] mentioned that the muscles protein content was decreased while that of fat and Pb contents in the fish muscles were increased in proportion to the pollution levels.…”

“…In the same line Salem, concluded that Cd and Pb negatively affected fish body gain, protein efficiency ratio, chemical composition and muscles area [3]. These two metals were found to be responsible for different types of chromosomal aberrations and lower mitotic index in the fish [52]. Demuynck added that cadmium-binding protein level in the cells of intestine was increased after exposure to Cd, so it appears that this protein will be synthesized as a response to Cd over exposure [52].…”

Effects of copper and other metals on fertilization, embryo development, larval survival and settlement of the polychaeteNereis (Neanthes) virens

“…It is not clear why N. virens larvae are less tolerant to copper than other species and that the nectochaete stage is much less tolerant than an adult. Polychaetes can excrete, sequester or detoxify significant concentrations of heavy metals using a number of mechanisms including binding metals to metallothioneins and myrohemythrins (Amiard et al, 2006;Demuynck et al, 2007). Differences among species in the efficacy of these mechanisms and that the larval stages may not have fully functioning systems may be responsible for the differences observed.…”

Towards an integrative soil health assessment strategy: A three tier (integrative biomarker response) approach with Eisenia fetida applied to soils subjected to chronic metal pollution

“…Troponin I is a part of the troponin complex, which has four binding sites for Ca2+ and Mg2+ and binds actin in thin myofilaments during muscle contraction, is present in the transversely and obliquely striated muscles of E. fetida (Royuela et al, 1996). The involvement of hemerythrins in metal detoxification is controversial (Demuynck et al, 2004) but they have been proposed to play a relevant role in Cd binding in the earthworm Allobophora caliginosa (Nejmeddine et al, 1997). Erythrocruorin is a cooperative oxygen-transporting protein that exists in free solution in blood of E. fetida (Pionetti and Pouyet, 1980).…”