Several members of the VEGF family have been described during the past few years, including VEGF-A, PlGF, VEGF-B, VEGF-C, VEGF-D, and VEGF-E. VEGF-
A is the original human VEGF and has multiple roles in the human body. All members of the family share the ability to enhance endothelial cell proliferation but are thought to have different roles in vascularization; VEGF-B is related to vascularization of skeletal muscle, and PlGF to that of the placenta. VEGF-E is the viral homolog of VEGF. In addition, VEGF-B and VEGF-D are associated with bone and tooth development, VEGF-C with lymphangiogenesis, and VEGF-A, VEGF-B, and VEGF-C have a role in tumor angiogenesis.
Alternative splicing from a single gene containing eight exons gives rise to at least five different isoforms of VEGF-A, containing 121, 145, 165, 189, and 206 amino acid residues. The isoforms are differentiated by the presence of peptides encoded by exons 6 and 7 of the VEGF gene. VEGF206 and VEGF189 contain both exons 6 and 7 (but differ in the number of amino acids), VEGF165 contains exon 7 only, VEGF145 contains exon 6 only, and VEGF121 lacks both exons. The best studied VEGF isoforms are VEGF121, VEGF165, and VEGF189, because of their abundance and the fact that they are usually produced simultaneously by VEGF-producing cells. VEGF145 and VEGF206 are rarer and less studied forms.
The VEGF isoforms differ in their heparin binding affinities. VEGF121 does not bind to heparin, whereas both VEGF165 and VEGF189 do, because of the presence of exons 6 and 7. The binding abilities of VEGF189 are higher, which has been explained by the presence of both exons.
Was this article helpful?
This ebook provides an introductory explanation of the workings of the human body, with an effort to draw connections between the body systems and explain their interdependencies. A framework for the book is homeostasis and how the body maintains balance within each system. This is intended as a first introduction to physiology for a college-level course.