Heparin protects heparin-binding growth factor-I from proteolytic inactivation in vitro

Area of Science:

• Biochemistry
• Molecular Biology
• Cell Biology

Background:

• Heparin-binding growth factor-I (HBGF-I) is susceptible to proteolytic degradation.
• Proteolytic inactivation limits HBGF-I's biological activity and stability.
• Understanding HBGF-I stability is crucial for its role in cell growth.

Purpose of the Study:

• To investigate the protective role of heparin against HBGF-I proteolytic digestion.
• To elucidate the mechanism by which heparin stabilizes HBGF-I.
• To determine if heparin influences HBGF-I's response to thermal denaturation.

Main Methods:

• Assessing HBGF-I digestion by proteases (trypsin, plasmin) with and without heparin.
• Evaluating the effect of thermal denaturation on HBGF-I stability in the presence of heparin.
• Utilizing autoradiography to track 125I-HBGF-I modification in human umbilical vein endothelial cells.

Main Results:

• Heparin significantly inhibits the proteolytic digestion of HBGF-I by various proteases.
• Heparin protects HBGF-I from thermal denaturation, preserving its structure and function.
• The protective effect of heparin is concentration-dependent and influenced by temperature and time.
• Heparin nearly completely protects HBGF-I from proteolytic modification in endothelial cell cultures.

Conclusions:

• Heparin protects HBGF-I from proteolytic inactivation, a key mechanism for increasing endothelial cell number.
• Heparin confers conformational stability to HBGF-I, reducing its susceptibility to denaturation.
• The heparin:HBGF-I structural interaction is primarily responsible for resistance to proteolysis.