Methods: Quantitative RT-PCR was used to determine the transcriptional activity of targeted genes after 3 h of contact between P. gingivalis ATCC 33277 (5 × 108 CFU/ml) and recombinant S. oralis ATCC 9811 GAPDH (rGAPDH; 100 μg/ml). Primers for P. gingivalis RagA4, AbfD, GAPDH, GDH, MDH, LuxS and FimA were prepared. Transcript levels were normalized to 16S rRNA. P. gingivalis in the absence of rGAPDH was used as a control. To investigate the expression level of P. gingivalis proteins, P. gingivaliscell surface GDH, MDH and NADH oxidase activities were measured spectrophotometrically.
Results: ragA4, abfD, and gdh showed significantly increased expression in P. gingivalis cultured with rGAPDH than in P. gingivalis alone. In contrast, the expression of gapdh and mdh was significantly lower in P. gingivalis cultured with rGAPDH than in the control. NADH oxidase activity and GDH activity on the cell surface of P. gingivalis were increased 3-fold and 2.4-fold by the presence of rGAPDH, respectively. P. gingivalis MDH cell surface activity with rGAPDH was 37.2% of the activity without rGAPDH. P. gingivalis luxS mRNA level was significantly increased when P. gingivalis was cultured with rGAPDH compared to that with P. gingivalis alone. However, P. gingivalis fimA mRNA levels were similar to the control.
Conclusions: These results indicate that oral streptococcal GAPDH may function as regulators in P. gingivalis protein expression.