Activation of protein kinase C modulates the adenylate cyclase effector system of B-lymphocytes.

Antibodies to surface immunoglobulins activate inositol phospholipid hydrolysis in B-lymphocytes, but very little is known concerning their effects on cAMP levels. In other cells, products from the hydrolysis of phosphatidylinositol 4,5-bisphosphate can increase and/or potentiate cAMP accumulation. In this study we have examined whether goat anti-mouse IgM (mu-chain-specific) stimulates and/or potentiates increases in the cAMP levels of splenocytes from athymic nude mice. Goat anti-mouse IgM, by itself, stimulated a 60% increase in cAMP within 2 min. Pretreating the cell suspensions at 37 degrees C with anti-IgM produced opposite effects on the forskolin- and prostaglandin E1 (PGE1)-induced increase in cAMP. Anti-IgM (25 micrograms/ml) potentiated the rise in cAMP induced by 100 microM forskolin 76%, but it decreased the response to 50 nM PGE1 by 30%. Direct activation of protein kinase C (Ca2+/phospholipid-dependent enzyme) by 12-O-tetradecanoylphorbol 13-acetate and/or sn-1,2-dioctanoylglycerol resulted in a similar pattern of responses. A 3-min preincubation with 97 nM 12-O-tetradecanoylphorbol 13-acetate potentiated the forskolin-induced response from 1.7 +/- 0.1 to 4.3 +/- 0.6 pmol of cAMP/10(6) cells but reduced the PGE1 response from 0.98 +/- 0.06 to 0.51 +/- 0.03 pmol of cAMP/10(6) cells. Similarly, preincubating the cells for 3 min with 5 microM sn-1,2-dioctanoylglycerol increased the forskolin response from 1.7 +/- 0.1 to 5.1 +/- 0.2 pmol of cAMP/10(6) cells but reduced the response to PGE1 from 1.15 +/- 0.03 to 0.75 +/- 0.04 pmol of cAMP/10(6) cells. Thus, activation of protein kinase C by hydrolysis products of inositol phospholipids, 12-O-tetradecanoylphorbol 13-acetate, or exogenous diacylglycerols modified adenylate cyclase itself and sites upstream of adenylate cyclase such as the receptor or G proteins coupling the receptor to the cyclase. Furthermore, modification of the PGE1 response by anti-IgM provides a mechanism by which antigen can differentially regulate T- and B-cells responding to macrophage-produced prostaglandins during an immune response.