Expression of a 70-kDa immunoreactive form of bile salt-dependent lipase by human pancreatic tumoral Mia PaCa-2 cells

This work describes the characterization of an immunoreactive form of bile salt-dependent lipase (BSDL) expressed by the human pancreatic tumoral Mia PaCa-2 cell line. This BSDL-related protein, which has an M-r of 70 kDa, is enzymatically active and poorly secreted. Furthermore, a protein with the same electrophoretic migration can also be immunoprecipitated with polyclon al antibodies specific for the human pancreatic BSDL after in vitro transla tion of RNA isolated fi-om Mia PaCa-2 cells. These data indicated that this BSDL related protein might be poorly, or not, glycosylated. Reverse transc ription and amplification of RNA extracted from Mia PaCa-2 cells using prim ers able to specifically amplify the full-length mRNA of the human BSDL res ulted in a detectable 1.8-kb cDNA product, shorter than that of BSDL (2.2 k b). The sequence of this transcript corresponds to the mRNA sequence that c odes for the mature human pancreatic BSDL. However, a deletion of 330 kp is located within the 3'-domain of this cDNA. Therefore data allowed us to co nclude that the 70-kDa BSDL-related protein is a 612 amino acid length prot ein and represents a truncated form of BSDL. The deletion of 110 amino acid s occurs in the C-terminal region of the protein, which encompasses 6 tande mly repeated sequences instead of the 16 normally present in the sequence o f BSDL. Because feto acinar pancreatic protein (FAPP), which is the oncofet al counterpart of BSDL, is a C-terminally truncated isoform of BSDL, it is suggested that the 70-kDa BSDL-related protein expressed in MiaPaCa-2 cells could be representative of the protein moiety of FAPP. (C) 2000 Academic P ress.