Changes in
transglutaminase (TG) activity in superior cervical ganglia (SCG) and nodose ganglia (NG) excised from adult rats were examined following application of selected membrane transport-altering agents, including GM1-ganglioside (GM1) and
alpha-sialylcholesterol (alpha-SC). Although TG activity of freshly dissected SCG and NG was relatively low, it increased gradually during 30 min of incubation, and it stayed at this elevated level for 2 h. Addition of alpha-SC at its maximal effective concentration, 20 microM, stimulated TG activity more than eightfold in SCG and more than twofold in NG by 30 min. Addition of GM1 at its most effective concentration, 5 nM, had similar effects, but of lesser magnitude.
Cycloheximide, a potent inhibitor of protein biosynthesis, did not affect the GM1- or alpha-SC-evoked increases in ganglionic TG activity, suggesting that enzyme activation rather than synthesis of new
enzyme was occurring. The stimulation of TG activity in both ganglia caused by either GM1 or alpha-SC was associated with a decrease in Km and an increase in Vmax values. Addition of
cholera toxin B, which specifically masks the
oligosaccharide chain of GM1, reduced the GM1-induced increase in TG activity by approximately 60% in SCG and 88% in NG. The alpha-SC-induced increase in TG activity was only partially mimicked by free
cholesterol. Although application of either
dibutyryl cyclic AMP or
dibutyryl cyclic GMP produced little change in TG activity of either
ganglion,
phorbol ester clearly inhibited the enzymic activity. Because TG is a
calcium-dependent
enzyme, we measured 45Ca2+ influx into either
ganglion, and found that it was reduced by GM1 and alpha-SC in SCG and by alpha-SC in NG.(ABSTRACT TRUNCATED AT 250 WORDS)