Suppression and overexpression of adenosylhomocysteine hydrolase-like protein 1 (AHCYL1) influences zebrafish embryo development - a possible role for AHCYL1 in inositol phospholipid signaling

Adenosylhomocysteine hydrolase-like protein 1 (AHCYL1)1 is a novel intracellular protein with ~50% protein identity to adenosylhomocysteine hydrolase (AHCY), an important enzyme for metabolizing S-adenosyl-L-homocysteine, the byproduct of S-adenosyl-L-homomethionine-dependent methylation. AHCYL1 binds to the inositol 1,4,5-trisphosphate receptor (IP3R), suggesting that AHCYL1 is involved in intracellular calcium release. We identified two zebrafish AHCYL1 orthologs (zAHCYL1A and B) by bioinformatics and reverse transcriptase-polymerase chain reaction (RT-PCR). Unlike the ubiquitously present AHCY genes, AHCYL1 genes were only detected in segmented animals and AHCYL1 proteins were highly conserved among species. Phylogenic analysis suggested that the AHCYL1 gene diverged early from AHCY and evolved independently. Quantitative RT-PCR showed that zAHCYL1A and B mRNA expression was regulated differently to the other AHCY-like protein zAHCYL2 and zAHCY during zebrafish embryogenesis. Injection of morpholino antisense oligos against zAHCYL1A and B into zebrafish embryos inhibited zAHCYL1A and B mRNA translation specifically and induced ventralized morphologies. Conversely, human and zebrafish AHCYL1A mRNA injection into zebrafish embryos induced dorsalized morphologies that were similar to those obtained by depleting intracellular calcium with thapsigargin. hAHCY mRNA injection showed little effect on the embryos. These data suggest that AHCYL1 has a different function from AHCY and plays an important role in embryogenesis by modulating IP3R function for the intracellular calcium release.