Identification of protein phosphatase 2A as the primary target for microcystin‐LR in rat liver homogenates
- 16 May 1994
- journal article
- Published by Wiley in FEBS Letters
- Vol. 344 (2-3), 175-180
- https://doi.org/10.1016/0014-5793(94)00382-3
Abstract
The liver-specific toxin microcystin-LR (MC-LR) is a potent inhibitor of type 1 (PP1) and type 2A (PP2A) protein phosphatases. A tritiated form of the toxin, [3H]dihydromicrocystin-LR ([3H]DMC-LR), was used to identify target proteins in cellular fractions prepared from rat liver homogenates. About 80% of the [3H]DMC-LR bound to proteins was in the cytosolic fraction, which contained essentially all of the PP2A. In contrast, much of the PP1 was found in particulate fractions, each with only a few percent of the total protein-bound [3]HDMC-LR. Protein-bound [3H]DMC-LR in the cytosol co-eluted with PP2A, but not with PP-1 from a DEAE-Sepharose column. Native forms of liver cytoplasmic PP2A and PP1 separated by aminohexyl-Sepharose adsorption showed similar sensitivity to inhibition by MC-LR, and bound [3H]DMC-LR proportional to the amount of phosphatase activity. The results indicate that [3H]DMC-LR can bind both PP2A and PP1 in the liver which must be important for microcystin-induced toxicity, but is recovered mainly bound to PP2A in the cytosol.Keywords
This publication has 36 references indexed in Scilit:
- Co-crystallization of the Catalytic Subunit of the Serine/Threonine Specific Protein Phosphatase 1 from Human in Complex with Microcystin LRJournal of Molecular Biology, 1994
- The interaction of SV40 small tumor antigen with protein phosphatase 2A stimulates the map kinase pathway and induces cell proliferationCell, 1993
- Cytoskeletal changes in hepatocytes induced by Microcystis toxins and their relation to hyperphosphorylation of cell proteinsChemico-Biological Interactions, 1992
- Association of microcystin‐LR and its biotransformation product with a hepatic‐cytosolic proteinJournal of Biochemical Toxicology, 1991
- Rapid purification of protein phosphatase 2A from mouse brain by microcystin‐affinity chromatographyFEBS Letters, 1991
- Hepatocyte deformation induced by cyanobacterial toxins reflects inhibition of protein phosphatasesBiochemical and Biophysical Research Communications, 1990
- In vitro and in vivo effects of protein phosphatase inhibitors, microcystins and nodularin, on mouse skin and fibroblastsBiochemical and Biophysical Research Communications, 1990
- Cyanobacterial microcystin‐LR is a potent and specific inhibitor of protein phosphatases 1 and 2A from both mammals and higher plantsFEBS Letters, 1990
- THE STRUCTURE AND REGULATION OF PROTEIN PHOSPHATASESAnnual Review of Biochemistry, 1989
- Calyculin A and okadaic acid: Inhibitors of protein phosphatase activityBiochemical and Biophysical Research Communications, 1989