Expression of MarvelD3 in epithelial cell lines. (A) Endogenous levels of MarvelD3 proteins in Caco-2 and HCE cells. The two cell lines were transfected with the indicated concentrations of siRNAs, using a pool of the four MarvelD3-directed siRNAs. After cell lysis, expression levels of MarvelD3 and α-tubulin were analysed by immunoblotting. (B) Identification of functional siRNAs. Caco-2 cells were transfected with individual siRNAs targeting MarvelD3 or control siRNAs. Depletion of MarvelD3 was then analysed by immunoblotting. (C) Exogenous expression of MarvelD3 isoforms. Caco-2 cells were transfected with cDNAs encoding either isoform 1 or isoform 2 of MarvelD3. Expression was then analyzed by immunoblotting with anti-MarvelD3 antibody. MD3_1 and MD3_2 constructs were run on separate SDS-PAGE gels and are shown alongside control transfections run on the same gels. Note, endogenous levels of MarvelD3 are only detected at longer exposures than those used to detect transfected proteins.