Brain fibroblast growth factor: nonidentity with myelin basic protein fragments

Area of Science:

• Biochemistry
• Cell Biology
• Molecular Biology

Background:

• Fibroblast growth factor (FGF) from bovine brain was previously thought to be derived from myelin basic protein (MBP).
• Limited proteolysis of MBP was proposed to generate active FGF polypeptide fragments.

Purpose of the Study:

• To investigate the true origin and mitogenic activity of bovine brain FGF.
• To determine if MBP fragments possess the reported FGF activity.

Main Methods:

• Acid protease digestion of bovine MBP.
• Assay of mitogenic activity via [3H]thymidine incorporation in BALB/c 3T3 cells.
• Isoelectric focusing and affinity chromatography (chicken anti-bovine MBP-Sepharose) for protein characterization.

Main Results:

• Acid protease-generated bovine MBP fragments showed no mitogenic activity.
• The principal active component of brain FGF preparation had a pI of 4.8-5.8, distinct from MBP fragments (pI ~10).
• The active FGF component did not bind to anti-bovine MBP-Sepharose, confirming it is not MBP-derived.

Conclusions:

• The mitogenic activity of bovine brain FGF is not attributable to myelin basic protein fragments.
• Previous reports likely misidentified MBP fragments as FGF due to co-purification.
• Further purification (50-100 fold) is necessary to isolate homogeneous, biologically active brain FGF.