The synthetic undecameric
peptide,
pGlu-Pro-Pro-Gly-Gly-Ser-Lys-Val-Ile-Leu-Phe, known as the
hydra head activator peptide, present in high concentrations in mammalian hypothalamus and intestine, was tested for neurotrophic activity in a survival assay using cultured chick embryonic sympathetic and dorsal root ganglion cells, and for morphological differentiation activity on
neuroblastoma cells.
Hydra head activator peptide supported neuron survival. The optimal active concentration, 1 pM, was very similar to the concentration that causes bud and head formation in hydra. Maximal neuron survival obtained with
hydra head activator peptide was close to that obtained with
nerve growth factor: both substances enhanced survival up to 3 times that of control cultures.
Bradykinin, which has some amino acid sequence homology with hydra head activator, was inactive as a
neurotrophic factor. Hydra head activator induced rapid morphological differentiation of the mouse
neuroblastoma cell line Neuro-2A. Neuro-2A responded to the
peptide by process extension, 4 h after its addition to the culture medium.
Neurotrophic factors isolated to date have been characterized by their ability to maintain cell viability and enhance neurite outgrowth.
Hydra head activator peptide met these two criteria when tested in 3 different neuron culture systems. Our results suggest that the
head activator peptide may act as a
neurotrophic factor for neurons in other species, including mammals.