Signal transduction for cecropin B gene expression in adherent hemocytes of the silkworm, Bombyx mori (Lepidoptera: Bombycidae)

Expression of a cecropin gene of Bombyx mori (B. mori) in isolated hemocytes was triggered in vitro by lipopolysaccharide (LPS), dibutyrylcyclic AMP (dcAMP), Vibrio cholerae (V.c.) toxin, ionomycin and 4 beta-phorbol 12-myristate 13-acetate (PMA), suggesting that cyclic AMP (cAMP), G protein, Ca2+ and protein kinase C (PKC) might be involved in expression of the gene. Inhibitors such as H-7 and H-89, but not genistein, greatly suppressed cecropin gene activation by LPS, strongly suggesting that PKC and protein kinase A (PKA), but not tyrosine kinases, may participate in the signal transduction. Conversely, other serine/threonine kinase inhibitors such as W-7 and KN-62 showed only weak suppression. This result suggested that myosin light chain kinase and Ca2+/calmodulin dependent protein kinase did not play a significant role in cecropin B gene activation. The inhibition of the induction by cycloheximide indicated that a certain protein factor with a high turnover rate may be indispensable for cecropin B gene expression triggered by LPS.