calyculin-a and dephostatin

Interaction between p38MAPK and p42/44MAPK in rat pinealocytes was examined by determining the effects of p38MAPK inhibitors on the phosphorylation of p42/44MAPK using Western blot analysis. Treatment with SB202190, a specific inhibitor of p38MAPK, increased p42/44MAPK phosphorylation in a concentration-dependent manner. SB202190 also enhanced the magnitude and the duration of norepinephrine-activated p42/44MAPK phosphorylation. The effect of SB202190 on p42/44MAPK phosphorylation was abolished by PD98059 or UO126, inhibitors of MEK, suggesting that SB202190 is acting upstream of MEK in activating p42/44MAPK. The SB202190-induced phosphorylation of p42/44MAPK was not blocked by inhibitors of cGMP-dependent kinase (KT5823), protein kinase C (calphostin C) or Ca2+/calmodulin dependent kinase (KN93) suggesting that these pathways may not be involved in the effect of SB202190. SB202190 further increased p42/44MAPK phosphorylation that was stimulated by 8-bromo-cGMP, 4beta phorbol 12-myristate 13-acetate, or ionomycin. In contrast, inhibition of p42/44MAPK phosphorylation by dibutyryl-cAMP persisted when p42/44MAPK phosphorylation was increased by SB202190. Furthermore, inhibition of p42/44MAPK phosphorylation had no effect on p38MAPK activation. These results suggest that inhibition of p38MAPK causes activation of p42/44MAPK and acts synergistically with norepinephrine in the regulation of p42/44MAPK activation in rat pinealocytes.

Topics: Animals; Enzyme Activation; Enzyme Inhibitors; Gene Expression; Hydroquinones; Imidazoles; Marine Toxins; Mitogen-Activated Protein Kinase 1; Mitogen-Activated Protein Kinases; Norepinephrine; Oxazoles; p38 Mitogen-Activated Protein Kinases; Phosphoprotein Phosphatases; Phosphorylation; Pineal Gland; Pyridines; Rats; Rats, Sprague-Dawley

Lactacystin (1.3 microM), a metabolite from an actinomycete, induced the formation of bipolar projections at both sides of the cell body of Neuro 2a cells 1 day after treatment and networks at and after 3 days and enhanced acetylcholinesterase activity (a marker of neuronal differentiation). Thus, the neuronal differentiation was characterized both morphologically and functionally. The experiments with various inhibitors of protein kinases and phosphatases revealed that the protein phosphatase inhibitors calyculin A (0.5 nM) and okadaic acid (0.6 nM) inhibit the formation of bipolar projections at 1 day, but does not inhibit the network formation at and after 3 days.

Topics: Acetylcholinesterase; Acetylcysteine; Animals; Antifungal Agents; Biomarkers; Bucladesine; Cell Differentiation; Cell Line; Cysteine Proteinase Inhibitors; Enzyme Inhibitors; Ethers, Cyclic; Hydroquinones; Kinetics; Marine Toxins; Neurites; Neurons; Okadaic Acid; Oxazoles; Phosphoprotein Phosphatases; Protein Kinase Inhibitors; Pyrans; Spiro Compounds; Time Factors