Basal membrane permeability of epithelial cells from the lower third and the middle of rat colonic crypts is dominated by a K+ conductance as shown by ion replacement experiments. Calyculin A, an inhibitor of protein phosphatases, induced a depolarization of these cells. The depolarization was concomitant with an inhibition of membrane current. The current inhibited by calyculin A had a reversa...

We have recently reported that Ser/Thr phosphatases play a key role in regulating natural killer (NK) cell lytic activity and that calyculin A and okadaic acid affect this activity differently [Bajpai and Brahmi (1994) J. Biol. Chem. 269, 18864-18869]. Here, we investigate a mechanism that might account for this differential action of calyculin A and okadaic acid on NK cells. Calyculin A specif...

Phosphodiesterase type 3B (PDE3B) has been shown to be activated and phosphorylated in response to insulin and hormones that increase cAMP. In order to study serine/threonine protein phosphatases involved in the regulation of rat adipocyte PDE3B, we investigated the phosphorylation and activation of PDE3B in vivo in response to phosphatase inhibitors and the dephosphorylation and deactivation o...

Calyculin A, a protein phosphatase inhibitor, induced cleavage-like morphological change in unfertilized sea urchin eggs. A contractile ring-like apparatus containing both filamentous actin and myosin was formed in the cleavage furrow. Wheat germ agglutinin receptors were also found in the same region. The eggs did not develop further after constriction of the ring. No aster-like microtubular s...

We have previously shown that rat thyroid FRTL-5 cells express a calcium entry pathway regulated by a phosphatase. The nature of the calcium entry pathway is presently unknown. We have also shown that FRTL-5 cells express only the TRPC2 channel of the TRPC family of cation channels. In the present investigation we show, using pharmacological inhibitors, the measurement of sodium and calcium ent...

BACKGROUND/AIMS The serine/threonine protein phosphatase 1 and 2a inhibitor Calyculin A may trigger suicidal death or apoptosis of tumor cells. Similar to apoptosis of nucleated cells, erythrocytes may enter eryptosis, the suicidal erythrocyte death characterized by cell shrinkage and cell membrane scrambling with phosphatidylserine translocation to the erythrocyte surface. Triggers of eryptosi...

Protein phosphorylation plays many important roles in cell functions and cell differentiation. To clarify the roles of protein phosphorylation in early embryonic development in mice, 2-cell embryos were cultured in the presence of various protein phosphatase inhibitors such as calyculin A, okadaic acid, cyclosporin A, tacrolimus (FK506) and benzyl-phosphonic acid. Calyculin A potently inhibited...

The effects of the phosphatase inhibitors calyculin A and okadaic acid on amylase release from streptolysin-O permeabilized rat pancreatic acini were investigated. Both agents induced similar biphasic effects with moderate potentiation of calcium-stimulated amylase release at medium and strong inhibition at higher concentrations. Calyculin A was thirty times more potent than okadaic acid and at...

Arachidonic acid (AA) regulates intracellular calcium concentration ([Ca2+]i) in a variety of cell types including salivary cells. In the present study, the effects of serine/threonine phosphatases on AA-induced Ca(2+) signaling in mouse parotid acini were determined. Mice were euthanized with CO2. Treatment of acini with the serine/threonine phosphatase inhibitor calyculin A blocked both thaps...

Plasmodium falciparum is transmitted from humans to Anopheles mosquito vectors via the sexual erythrocytic forms termed gametocytes. Erythrocyte filtration through microsphere layers (microsphiltration) had shown that circulating gametocytes are deformable. Compounds reducing gametocyte deformability would induce their splenic clearance, thus removing them from the blood circulation and blockin...