The head activator is released from regenerating Hydra bound to a carrier molecule

Abstract

Hydra forced to regenerate a head releases head activator and head inhibitor during the first hours after cutting to induce head‐specific growth and differentiation processes. Analysis of the size distribution demonstrated that the head‐activator peptide is co‐released with (a) large molecular weight carrier molecule(s) to which it is non‐covalently bound. The carrier‐bound head activator is fully active on Hydra indicating that a carrier does not hinder the interaction with receptors. In contrast to this the head inhibitor is released in its naked, low molecular mass form. The association or non‐association with a carrier molecule results in marked differences in biological properties. The head activator has a short range of action, but a long half‐life, the head inhibitor has a global range of action, but a short half‐life. These results provide a plausible explanation why two antagonistically acting substances, although they are released from the same site and simultaneously nevertheless can give rise to a well‐defined temporal and spatial pattern of differentiation as occurs, for example, during head regeneration in Hydra.

The neuropeptide head activator loses its biological acitivity by dimerization.

“…In physiological systems endogeneous HA is stabilized in the monomeric form by being bound to a carrier molecule (Roberge, 1985;Schaller et al, 1986). This loss in biological activity, which was most pronounced after chromatography on reversed phase C8 or C18 columns, was not accompanied by a corresponding loss of peptide as evidenced by quantitative amino acid analysis.…”

“…Endogenous HA is released from regenerating Hydra bound to a carrier molecule (Roberge, 1985;Schaller et al, 1986). This HA is biologically active indicating that it is bound to and released from the carrier as monomer.…”

Head activator acts as an autocrine growth factor for NH15-CA2 cells in the G2/mitosis transition.

“…Medium conditioned for 2 days by cells at subconfluency density contained up to nanomolar concentrations of HA. This HA was, as in hydra, released bound to a carrier complex (Roberge, 1985;Schaller et al, 1986) from which the HA peptide could be liberated by methanol or salt extraction. This HA peptide eluted from HPLC C18 columns at the same position as tritiated synthetic HA (Figure 2), reacted with all the HA antibodies that HA did, and had the same amino acid composition as HA.…”

Induction and Fixation of Polarity — Early Steps in Plant Morphogenesis

“…Transplanation and fusion experiments have shown two antiparallel subpolarities for animal-vegetative polarity of sea urchin eggs (1 1 , 47, 11 8) and amphibian embryos (33, 46, 121), for prestalk-prespore polarity in Dictyostelium (1 27), and for head-foot polarity in Hydra (10). In Dictystelium (127), as well as in Hydra (44,75,108), the substances involved in the induction of the subpolarities have been identified. Genetic analyses of anteroposterior and dorsoventralpolarity in Drosophila have revealed complex polarities (2,25,26,50,62,87).…”