Homocysteine increases methionine synthase mRNA level in Caco-2 cells.
BACKGROUND
Methionine synthase (MTR) synthesizes methionine from homocysteine, using cobalamin as a cofactor and 5-methyltetrahydrofolate as a cosubstrate.


OBJECTIVE
To determine the influence of homocystine (Hcy, dimer of homocysteine) in the presence of either cobalamin or methionine on the transcription and the activity of methionine synthase in Caco-2, a human adenocarcinoma cell line.


METHODS
Methionine synthase activity and quantification of its mRNA by real-time RT-PCR were determined in cells cultivated under four differents conditions: Hcy with cobalamin (Hcy+ Cbl+), Hcy with methionine (Hcy+Met+), methionine with Cbl (Met+ Cbl+) and methionine only (Met+).


RESULTS
Activity (nmol/h/mg protein) was maximal in cells cultivated in Hcy+Cbl+ (2.45 +/- 0.35), compared to cells cultivated in Hcy+Met+ (0.18 +/- 0.01, p<0.001), in Met+ Cbl+ (1.60 +/- 0.06, p<0.05), and in Met+ (0.40 +/- 0.05, p<0.001), suggesting an adaptation of the cells to requirement in synthesized methionine. The mRNA level of MTR in Hcy+ Cbl+ and Hcy+Met+ (2.82 +/-0.49 and 3.33 +/- 0.48 AU, respectively ) was about 2.5 / 3.0-fold higher than that in Met+ Cbl+ and in Met+ (1.00 +/-0.13 and 1.20 +/-0.20 AU, respectively, p<0.001).


CONCLUSIONS
Methionine synthase expression of Caco-2 cell is under a transcriptional control influenced by Hcy.
Laboratoire de Pathologie Cellulaire et Moléculaire en Nutrition, Equipe INSERM 0014, Faculté de Médecine, Vandoeuvre-les-Nancy, France.
Sandrine
S
Ortiou
Jean-Marc
JM
Alberto
Jean-Louis
JL
Guéant
Marc
M
Merten
D013766:5-Methyltetrahydrofolate-Homocysteine S-Methyltransferase / Q000032:analysis / Q000096:biosynthesis / Q000235:genetics*; D000230:Adenocarcinoma / Q000737:chemistry / Q000201:enzymology / Q000235:genetics*; D018938:Caco-2 Cells; D015972:Gene Expression Regulation, Neoplastic; D006710:Homocysteine / Q000494:pharmacology / Q000502:physiology*; D006801:Humans; D008715:Methionine / Q000494:pharmacology / Q000502:physiology; D012333:RNA, Messenger / Q000032:analysis / Q000378:metabolism; D014158:Transcription, Genetic / Q000235:genetics; D015854:Up-Regulation; D014805:Vitamin B 12 / Q000494:pharmacology / Q000502:physiology
D012333:RNA, Messenger; D006710:Homocysteine; D008715:Methionine; D013766:5-Methyltetrahydrofolate-Homocysteine S-Methyltransferase; D014805:Vitamin B 12