Gene identification and evidence for expression of G protein α subunits, phospholipase C, and an inositol 1,4,5-trisphosphate receptor in Aplysia californica rhinophore

Abstract

In the marine mollusk Aplysia californica, waterborne protein pheromones that are released during egg laying act in concert to stimulate mate attraction. However, molecular information concerning the cellular receptors and signaling mechanisms that may be involved in waterborne peptide and protein pheromonal communication is lacking. As a first step toward examining whether members of the G protein family and phosphoinositide signaling pathway are present in the primary peripheral chemosensory organs (i.e., rhinophores), we isolated five full-length cDNA clones from an A. californica central nervous system cDNA library. These clones encoded (1) the G protein alpha subunits of the Gq, Gi, and Go families, (2) a protein with homology to phospholipase C (PLC) isoforms, and (3) an inositol 1,4,5-trisphosphate receptor (IP3R). The expression of these genes was examined using laser capture microdissection/reverse transcription-polymerase chain reaction and in situ hybridization. All of them are expressed in the rhinophore sensory epithelium, suggesting that Galphaq, Galphai, Galphao, PLC-like protein, and IP3R may be involved in waterborne protein pheromone detection in Aplysia-possibly via a phosphoinositide signaling mechanism.

Molecular identification of candidate chemoreceptor genes and signal transduction components in the sensory epithelium ofAplysia

“…Finally, Aplysia Ins(1,4,5)P 3 R cDNA encodes a 2762-residue protein with an estimated molecular mass of 315 kDa that shares a high degree of identity with invertebrate Ins(1,4,5)P 3 R homologs. Consistent with a potential role in Aplysia chemical transduction, recent observations using laser capture microdissection of rhinophore sensory epithelium followed by G protein-, PLC-or Ins(1,4,5)P 3 Rspecific RT-PCR, indicate that these mRNA are expressed in rhinophore sensory epithelium (Cummins et al, 2007).…”

“…For the purpose of this study, we focused on PLC as a potential secondary signaling olfactory component because of recent identification of an Aplysia californica PLC homolog (Cummins et al, 2007). Fig.…”

“…4A. Extensive screening of a CNS cDNA library suggests that only one Aplysia Ins(1,4,5)P 3 R exists (Cummins et al, 2007). Immunoblot and immunohistochemical analyses were performed using affinity-purified Aplysia Ins(1,4,5)P 3 R antiserum.…”

“…Although relatively little is currently known about the molecular mechanism of chemical detection in molluscs, including the identity of chemoreceptors, recent olfactory studies in squid have shown that in olfactory receptor neurons, both phospholipase c (PLC) and cAMP-mediated pathways may be involved in signal processing (Mobley et al, 2007). In our studies of the marine opisthobranch mollusk Aplysia californica, we isolated a full-length cDNA from a central nervous system (CNS) cDNA library that encodes a protein homologous to the G protein alpha subunit G q (DQ397515), as well as a phospholipase C (PLC; DQ397516) and an inositol 1,4,5-trisphosphate receptor (Ins(1,4,5)P 3 R; DQ397517) (Cummins et al, 2007). The Aplysia Gα q gene encodes a protein of 353 amino acids, and shares conservation of myristoylation, palmitoylation and ADP-ribosylated sites with known G protein homologs.…”

A Novel Postsynaptic Mechanism for Heterosynaptic Sharing of Short-Term Plasticity

“…7, bottom right). To directly examine a possible interaction between ApHomer and Aplysia IP 3 R, we determined the coding sequence for the initial 154 amino acids of ApIP 3 R. A cDNA for Aplysia IP 3 R has also been reported, matching the sequences we obtained (Cummins et al, 2007). The consensus sequence for Homer binding is PXXFr (Tu et al, 1998), and in rat IP 3 R is found at amino acid positions 49–54.…”