The expression of transmembrane and
ubiquitin-like domain containing 1 (Tmub1) is upregulated during liver regeneration, however, the function and underlying molecular mechanisms responsible for Tmub1 action remain to be determined. This study utilized BRL-3A rat liver cells for Tmub1
shRNA lentivirus infection and
IL-6 stimulation. Semi-quantitative RT-PCR and western blot analysis were used to detect
mRNA and
protein expression levels, respectively. A [3H]
thymidine incorporation assay was performed to assess changes in cell proliferation rates.
Laser scanning confocal microscopy and immunoprecipitation-western blotting were used to assess the interaction between Tmub1 and
calcium-modulating
cyclophilin ligand (CAML)
protein. The effect of Tmub1 on
calcium ion influx into BRL-3A cells was measured by inverted fluorescence microscopy. The data showed that
IL-6 treatment induced proliferation of rat hepatocytes and expression of Tmub1
mRNA and
protein, while Tmub1
shRNA knocked down Tmub1 expression at both the
mRNA and
protein levels. Furthermore, compared to the negative control, Tmub1
shRNA-infected BRL-3A cells were highly proliferative with or without
IL-6 stimulation. Tmub1 is colocalized with CAML in the hepatocellular cytoplasm, whereas knockdown of Tmub1 expression upregulated expression of CAML
protein. Influx of Ca2+ into rat liver cells was also affected after Tmub1 knockdown. The data from the current study demonstrate that Tmub1 plays a negative role in IL-6-induced hepatocyte proliferation, and indicate that the interaction between Tmub1 and CAML may mediate the function of Tmub1 in hepatocytes.