VGF protein is a neurosecretory protein originallyidentified as a product of the nerve growth factor responsivegene Vgf in rat pheochromocytoma PC12 cells [, ]. VGF may be involved in the regulation of cell-cell interactions or in synatogenesis during the maturation of the nervous system []. Neuroendocrine regulatory peptides (NERP)-1 and NERP-2 are bioactive peptides processed from VGF and involved in the control of body fluid homeostasis by regulating vasopressin release. Administration of NERPs suppresses hypertonic saline- or angiotensin II-induced vasopressin release from the hypothalamus and pituitary [].
Virus-encoded growth factors (GF) are important for the virulence of poxviruses. They act to promote the growth of their host cell through their binding to host ErbB receptor tyrosine kinases, which in turn activate the MAPK pathway. These growth factors are related to mammalian epidermal growth factor (EGF), one of several host ErbB ligands. The viral GFs are potent mitogens, acting to prevent host receptor degradation and ubiquitination, which leads to sustained signal transduction. Growth factors from different poxviruses display unique patterns of specificity to host ErbB receptors: VGF (vaccinia virus GF) binds primarily to ErbB-1 homodimers, MGF (myxoma virus GF) binds to ErbB-2/ErbB-3 heterodimers, and SFGF (Shope fibroma virus GF) binds to different ErbB receptors [].
