Proliferative effects of gamma-aminobutyric acid on the gastric cancer cell line are associated with extracellular signal-regulated kinase 1/2 activation.
OBJECTIVE
Gamma-aminobutyric acid (GABA) is the principal inhibitory neurotransmitter in the adult mammalian brain. However, GABA is found not only in peripheral neuronal tissue, but also in many peripheral non-neuronal tissues, and is thought to have important physiological functions in addition to neurotransmission. We previously reported that GABA participates in chondrocyte proliferation. In the present study, we investigated the effects of GABA on the proliferation of a gastric cancer cell line, KATO III.


METHODS
Reverse transcription polymerase chain reaction and immunohistochemical analyses were performed to examine the expression of the GABA synthesis enzyme, glutamate decarboxylase (GAD), and that of the GABA(A) and GABA(B) receptor subunits. The production of GABA was confirmed by immunohistochemistry. The proliferative effect of GABA on KATO III cells was analyzed by bromodeoxyuridine incorporation assay, and the activation status of mitogen-activated protein (MAP) kinases (extracellular signal-regulated kinase [ERK]-1/2, Jun-N-terminal kinase, and p38) and the expression of cyclin D1 were analyzed by western blotting.


RESULTS
KATO III cells expressed GAD and GABA. More than five GABA(A) receptor subunits, including the pi subunit, were expressed in KATO III cells; however, GABA(B) receptor subunits were not seen. The addition of GABA to the medium promoted KATO III proliferation, and maximum proliferative effects were observed in the presence of 10 or 1 microM GABA. The addition of 1 microM GABA predominantly activated ERK-1/2 among the three MAP kinases in addition to increasing cyclin D1 expression.


CONCLUSIONS
GABA is able to promote KATO III cell proliferation in an autocrine or a paracrine fashion through GABA(A) receptors followed by MAP kinase activation.
Maemura
Kentaro
K
Department of Anatomy and Cell Biology, Division of Basic Medicine I, Osaka Medical College, Takatsuki, Osaka 569-8686, Japan. an2011@art.osaka-med.ac.jp
Shiraishi
Nanako
N
Sakagami
Kumiko
K
Kawakami
Ken
K
Inoue
Takuya
T
Murano
Mitsuyuki
M
Watanabe
Masahito
M
Otsuki
Yoshinori
Y
D045744:Cell Line, Tumor; D049109:Cell Proliferation; D019938:Cyclin D1 / Q000378:metabolism; D004789:Enzyme Activation; D015972:Gene Expression Regulation, Neoplastic; D005968:Glutamate Decarboxylase / Q000378:metabolism; D006801:Humans; D007150:Immunohistochemistry; D019950:Mitogen-Activated Protein Kinase 1 / Q000378:metabolism*; D048052:Mitogen-Activated Protein Kinase 3 / Q000378:metabolism*; D021122:Protein Subunits; D012333:RNA, Messenger / Q000378:metabolism; D011963:Receptors, GABA-A / Q000378:metabolism; D018080:Receptors, GABA-B / Q000378:metabolism; D020133:Reverse Transcriptase Polymerase Chain Reaction; D013274:Stomach Neoplasms / Q000201:enzymology* / Q000235:genetics / Q000473:pathology; D005680:gamma-Aminobutyric Acid / Q000378:metabolism*
C530104:CCND1 protein, human; D021122:Protein Subunits; D012333:RNA, Messenger; D011963:Receptors, GABA-A; D018080:Receptors, GABA-B; D019938:Cyclin D1; D005680:gamma-Aminobutyric Acid; D019950:Mitogen-Activated Protein Kinase 1; D048052:Mitogen-Activated Protein Kinase 3; D005968:Glutamate Decarboxylase; C402565:glutamate decarboxylase 1; C401141:glutamate decarboxylase 2