This paper presents an overview of the significance of the use of molecular biomarkers as diagnostic and prognostic tools for marine pollution monitoring. In order to assess the impact of highly persistent pollutants such as polychlorinated biphenyls (PCB), polychlorinated dibenzo-dioxins (PCDD), polychlorinated dibenzo-furans (PCDF), polynuclear aromatic hydrocarbons (PAH), tributyltin (TBT) and other toxic metals on the marine ecosystem a suite of biomarkers are being extensively used worldwide. Among the various types of biomarkers, the following have received special attention: cytochrome P4501A induction, DNA integrity, acetylcholinesterase activity and metallothionein induction. These biomarkers are being used to evaluate exposure of various species of sentinel marine organisms (e.g. mussels, clams, oysters, snails, fishes, etc.) to and the effect of various contaminants (organic xenobiotics and metals) using different molecular approaches [biochemical assays, enzyme linked immuno-sorbent assays (ELISA), spectrophotometric, fluorometric measurement, differential pulsed polarography, liquid chromatography, atomic absorption spectrometry]. The induction of the biotransformation enzyme, cytochrome P4501A in fishes (Callionymus lyra, Limanda limanda, Serranus sp., Mullus barbatus) and mussels (Dreissena polymorpha) by various xenobiotic contaminants such as PCBs, PAHs, PCDs is used as a biomarker of exposure to such organic pollutants. The induction of cytochrome P4501A is involved in chemical carcinogenesis through catalysis of the covalent bonding of organic contaminants to a DNA strand leading to formation of DNA adduct. Measurement of the induction of cytochrome P4501A in terms of EROD (7-ethoxy resorufin O-deethylase) activity is successfully used as a potential biomarker of exposure to xenobiotic contaminants in marine pollution monitoring. In order to assess the impact of neurotoxic compounds on marine environment the evaluation of acetylcholinesterase activity in marine organisms is used as a biomarker of exposure to neurotoxic agents such as organophosphorus, carbamate pesticides etc. Metallothioneins (MTs) are induced by toxic metals such as Cd, Hg, and Cu by chelation through cysteine residues and are used in both vertebrates and invertebrates as a biomarker of metal exposure. The measurement of the levels of DNA integrity in marine organisms such as Sea stars (Asterias rubens) from the North Sea and the marine snails (Planaxis sulcatus) from the Arabian Sea along the Goa coast exposed to environmental xenobiotic contaminants clearly indicated the extent and the nature of pollution at the sampling sites along coastal environment.

Extracellular a-synuclein (a-syn) assemblies can be up-taken by neurons; however, their interaction with the plasma membrane and proteins has not been studied specifically. Here we demonstrate that a-syn assemblies form clusters within the plasma membrane of neurons. Using a proteomic-based approach, we identify the a3-subunit of Na + /K + -ATPase (NKA) as a cell surface partner of a-syn assemblies. The interaction strength depended on the state of a-syn, fibrils being the strongest, oligomers weak, and monomers none. Mutations within the neuron-specific a3-subunit are linked to rapid-onset dystonia Parkinsonism (RDP) and alternating hemiplegia of childhood (AHC). We show that freely diffusing a3-NKA are trapped within a-syn clusters resulting in a3-NKA redistribution and formation of larger nanoclusters. This creates regions within the plasma membrane with reduced local densities of a3-NKA, thereby decreasing the efficiency of Na + extrusion following stimulus. Thus, interactions of a3-NKA with extracellular a-syn assemblies reduce its pumping activity as its mutations in RDP/AHC.