Objective: To identify and characterize the novel proteins encoded by a HCC-associated novel gene, LAPTM4B (lysosomeassociated protein transmembrane 4 beta).
Methods: The novel proteins was identified by Western blot, immunohistochemistry and 2D electrophoresis; the molecular interactions were studied by co-immunoprecipitation.
Results: LAPTM4B encoded two isoforms of proteins with molecular weight 35 x 10(3) and 24 x 10(3) and pI 9.07 and 4.65, respectively. The expression levels of LAPTM4B proteins in HCC tissues and cell lines were upregulated and related to differentiation, and most dramatically raised for 35 x 10(3) one. It was demonstrated that LAPTM4B--integrin alpha 6 and LAPTM4B--EGFR signaling complexes were formed when BEL-7402 cells were seeded on laminin substrate.
Conclusion: The LAPTM4B-35 protein is overexpressed in human HCC tissues and cell lines and may involve in signal transduction triggered by extracellular matrix via interaction with integrin alpha 6 and EGFR on cell surface.