The histamine H1 receptor activates the nitric oxide pathway at fertilization

Abstract

Sperm fusion with the egg initiates a signaling cascade that releases intracellular calcium (Ca(i) (2+)) from the endoplasmic reticulum (ER). In sea urchins, Ca(2+) is released as a single, large transient via two distinct pathways. The first depends on inositol 1,4,5-triphosphate (IP(3)) production and triggers the initial phase of Ca(2+) release, while the second depends on nitric oxide (NO) production and is thought to maintain the duration of the Ca(2+) wave. We identified a sea urchin homolog of the seven trans-membrane G protein-coupled receptor for histamine (suH(1)R) on the egg cell surface that activates NO production. Treatment with histamine (HA) causes fluctuations in the resting levels of NO in the egg, while antagonists or antibodies of H(1)R inhibit the rise of NO normally observed at fertilization. Inhibition of suH(1)R function decreases the maintenance, but not the amplitude, of the Ca(2+) transient and suggests that it is an integral part of the overall pathway leading to egg activation at fertilization in sea urchins.

Histamine is a modulator of metamorphic competence in Strongylocentrotus purpuratus(Echinodermata: Echinoidea)

“…In S. purpuratus, HA is an important signalling molecule during fertilization [41]. Antibodies specific to S. purpuratus H1R have shown that this receptor is present in the plasma membrane of the egg, and that activation of the receptor by HA sets off a signaling cascade resulting in intracellular calcium release [41].…”

“…Antibodies specific to S. purpuratus H1R have shown that this receptor is present in the plasma membrane of the egg, and that activation of the receptor by HA sets off a signaling cascade resulting in intracellular calcium release [41]. Here we test whether HA acts as a modulator of metamorphic competence by investigating the effects it has on pre-competent larvae.…”

Dissolved histamine: a potential habitat marker promoting settlement and metamorphosis in sea urchin larvae

“…to histamine suggests induction via an external histamine receptor, which is the expectation for a true metamorphic cue in nature. A sea urchin homologue of the metabotropic histamine H1 receptor of vertebrates (suH1R) has been identified on the surface of Strongylocentrotus purpuratus eggs, and this receptor is an integral part of the Ca2+ release pathway leading to fertilisation (Leguia and Wessel 2006). It is possible that suH1R is expressed in other sea urchins and may be involved in histamine-induced metamorphosis of sea urchin larvae, but this hypothesis requires further investigation.…”

Flipping the switch: How a sperm activates the egg at fertilization

“…A sea urchin homolog of the seven trans-membrane G protein-coupled receptor for histamine (suH 1 R) was recently identified on the cell surface of sea urchin eggs that leads to NO production (Leguia and Wessel, 2006). Treatment of eggs with histamine causes fluctuations in the resting levels of NO in the egg, while antagonists or antibodies of H 1 R inhibit the rise of NO normally observed at fertilization.…”