Species-specific high molecular weight forms of basic fibroblast growth factor

Area of Science:

• Biochemistry
• Molecular Biology
• Cell Biology

Background:

• Basic fibroblast growth factor (bFGF) is a key regulator of cell growth, differentiation, and survival.
• Previous studies have indicated potential variations in bFGF molecular weight, but a comprehensive species-specific analysis was lacking.

Purpose of the Study:

• To investigate and characterize the species-specific molecular forms of bFGF.
• To elucidate the molecular basis for observed differences in bFGF molecular weights across various species.

Main Methods:

• Extraction and partial purification of bFGF from diverse mammalian cell lines and brain tissues.
• Western blot analysis using species-specific and N-terminal antibodies.
• Ion-exchange chromatography (Cation exchange, Heparin-affinity, and Mono S) for protein separation.

Main Results:

• Detected species-specific bFGF forms with distinct apparent molecular weights across mouse, rat, human, and bovine sources.
• Identified 18 kDa, 21.5/22 kDa (rat/mouse), and 18 kDa, 22.5/24 kDa (human/bovine) bFGF variants.
• Confirmed that N-terminally extended forms of human bFGF correspond to the higher molecular weight variants (22.5 and 24 kDa).
• Demonstrated that molecular weight differences correlate with alternative translational start sites (ATG/CTG) in bFGF cDNAs.
• Successfully separated larger bFGF proteins from the 18 kDa form using Mono S chromatography.

Conclusions:

• Species of origin significantly influences the molecular weight of bFGF due to variations in translational initiation.
• The identified bFGF variants, including N-terminally extended forms, play distinct biological roles.
• Chromatographic methods like Mono S are effective for resolving different bFGF isoforms.