Heterologous signal peptides enable increasing titers of recombinant proteins in mammalian cell culture. Four human heterodimeric glycoprotein hormones (follicle-stimulating hormone, FSH
luteinizing hormone, LH
chorionic gonadotropin, CG
and thyroid-stimulating hormone, TSH) were expressed in stably transfected CHO cells when varying signal peptides of their β-subunits. The signal peptide of human serum albumin proved to be the most effective for the glycoprotein hormone family. The cell specific productivity was increased for LH (2.5 pg/cell, 4-fold increase), TSH (1.6 pg/cell, 13-fold increase), and CG (1.0 pg/cell, 60%-increase). According to the Western blotting and quantitative PCR data, the productivity increase is associated with an increase in the efficiency of translation and translocation of β-subunits of hormones in the endoplasmic reticulum due to their coupling with the heterologous signal peptides.