Ecotoxicology goes MudPIT?

Exposure to natural and anthropogenic compounds can potentially alter the proteome in body fluids and tissues of living organisms, and by applying proteomics it is possible to discover, identify and understand such alterations. This study show results from a proteomic approach where one- or multidimensional separation (MudPIT) combined with high-accuracy tandem mass spectrometry (i.e. LTQ Orbitrap) were used to identify proteins from a non-model organism (Salmo salar). An optimized two-dimensional method resulted in more than 680 proteins identified with high significance compared to 197 proteins identified using a one-dimensional separation. Thus, MudPIT proteomics greatly increase the number of successful protein identification studies in ecotoxicology, and could potentially provide more insight into chemical modes of actions.

Activation of the cAMP-dependent protein kinase signaling pathway by luteinizing hormone in trout theca layers.

In the fish ovary, LH is the main factor regulating the production of steroids during the periovulatory period and its effects are believed to be mediated, at least partially, through the cAMP-dependent protein kinase (PKA) signaling pathway. However, there is no direct evidence for the presence of PKA in the fish ovary nor on the regulation of its activity by fish LH. Here, we show the identification of regulatory (R) and catalytic (C) subunits of PKA in trout theca cells by immunoblotting. DEAE-cellulose chromatography of theca cell extracts indicated the presence of PKA type I and II and showed that trout theca cells display PKA-specific phosphotransferase and cAMP-binding activities. Salmon LH (sLH) stimulated PKA activity and increased the levels of immunoreactive RIIalpha, RIIbeta and C subunits in trout theca layers. These observations, coupled with the sLH-dependent decrease in the half-life of the C subunit, as shown by pulse-chase experiments, strongly suggest that sLH activates PKA in trout theca cells. Furthermore, our results suggest that ovarian PKA activity and its regulation by LH has been well conserved from fish to humans.