Laboratory of Molecular Immunology, National Heart, Lung, and Blood Institute, National Institutes of Health, Bethesda, Maryland 20892-1760, USA
Address for correspondence: Dr. Michael A. Beaven, Laboratory of Immunology, NHLBI, Room 8N109/Building 10, National Institutes of Health, Bethesda, MD 20896-1760. Voice: 301-496-6188; fax: 301-402-0171.
beavenm{at}nhlbi.nih.gov Abbreviations: ARF, ADP-ribosylation factor; BAD, Bcl-2/Bcl-X
L antagonist causing death; CaM, Ca
2+/calmodulin regulated; DNP-BSA, dintrophenylated bovine serum albumin—the antigen used in these studies along with DNP-specific IgE for sensitizing RBL-2H3 cells; Fc
RI, the high-affinity receptor for IgE; PK, protein kinase; PKI, peptide inhibitor of protein kinase A; PL, phospholipase; PMA, phorbol 12-myristate 13-acetate.
Ann. N.Y. Acad. Sci. 968: 198-212 (2002).
Functions attributed to phospholipase (PL) D include the regulation
of intracellular trafficking of Golgi-derived vesicles and secretion
of granules from mast cells. We have reported that activation
of PLD and secretion in a rat mast cell (RBL-2H3) line is substantially
enhanced by cholera toxin, a known activator of protein kinase
(PK) A. Here we review the evidence that (1) the synergistic
interactions of cholera toxin and other pharmacological agents
on mast cell secretion are attributable to the synergistic activation
of PLD via PKA, CaM kinase II, and PKC and (2) both PLD1 and
PLD2 participate in this process. For example, treatment with
cholera toxin, thapsigargin, and phorbol 12-myristate 13-acetate
(which activate PKA, CaM kinase II, and PKC, respectively) exhibit
synergy in the stimulation of both PLD and secretion. These
kinases and PLD are likely confined to membrane components,
as similar synergistic interactions could be demonstrated in
permeabilized cells. The regulation of PLD and secretion by
these kinases is also apparent from studies of inhibitors of
PKA and other kinases. Also, by overexpression of either PLD1
or PLD2 it is apparent that both isoforms respond to the same
stimuli as endogenous PLD, although PLD1 is largely associated
with secretory granules and PLD2 with plasma membrane. The studies
reveal interesting differences in the regulation of the translocation
of granules (regulated by PKA) and the fusion of these granules
with the plasma membrane (regulated by Ca
2+ and PKC). The pathological/physiological
implications of the regulation of PLD by PKA require further
evaluation in other cell systems.
