muramidase and 2-aminoethoxydiphenyl-borate

We have studied modulation of "store-operated calcium influx" by tyrosine phosphatases in the pancreatic acinar cell line AR42J and in HEK 293 cells. We show that inhibition of tyrosine phosphatases by bis-(N,N-dimethyl-hydroxamido) hydrooxovanadate (DMHV) leads to an increase in Ca(2+) release-activated Ca(2+) (CRAC) entry. This effect can be blocked in the presence of 2-aminoethyldiphenyl borate (2-APB). Furthermore, transfection of HEK 293 cells with the human wild-type tyrosine phosphatase PTP1B leads to inhibition of CRAC influx, whereas transfection with the substrate-trapping mutant of PTP1B (D181A) slightly increases Ca(2+) influx. It also decreases enzymatic activity of PTP1B as compared to non-transfected cells. Our data suggest that CRAC influx is modulated by tyrosine phosphorylation and dephosphorylation which involves the tyrosine phosphatase PTP1B.

Topics: Animals; Bombesin; Boron Compounds; Calcium; Calcium Channels; Cell Line; Cell Line, Tumor; Cytosol; Enzyme Inhibitors; Humans; Kinetics; Microscopy, Confocal; Microscopy, Fluorescence; Muramidase; Mutagenesis, Site-Directed; Mutation; Phosphorylation; Plasmids; Protein Tyrosine Phosphatase, Non-Receptor Type 1; Protein Tyrosine Phosphatases; Rats; Thapsigargin; Transfection; Vanadates