Secretion of GAWK, a Presumed Product of Chromogranin B Processing, by a Human Medullary Thyroid Carcinoma Cell Line: Effect of Phorbol Ester, Forskolin and Calcium-lonophore.
Abstract GAWK was isolated from human pituitary glands and presumed to be a processing product of human Chromogranin B. In the present studies, we investigated effects of phorbol ester (TPA), forskolin and Ca(2+)-ionophore (A23187) on GAWK secretion using a human medullary thyroid carcinoma-derived cell line (TT-cell). A dose-responsive stimulation of GAWK-like immunoreactivity (LI) secretion was found in the presence of TPA as well as forskolin. A23187 caused an increase of GAWK-LI secretion and addition of TPA together with A23187 revealed an additive effect on the GAWK-LI secretion. These findings indicate that GAWK-LI is a secretory peptide in the TT-cells and suggest that A and C kinase, and possibly Ca(2+)-calmodulin transduction systems are involved in the GAWK-LI secretion by the TT-cells. TT-cells may provide a good model for the investigation of regulation of Chromogranin secretion.
Iguchi
H
H
Department of Biochemistry, National Kyushu Cancer Center, Fukuoka 815, Japan.
Kameya
T
T
Kadoya
K
K
Shimaoka
K
K