Poster Presentation The Joint Annual Scientific Meetings of the Endocrine Society of Australia and the Society for Reproductive Biology 2017

Characterisation of a novel species-restricted putative hydroxysteroid dehydrogenase called HSD1L in the pituitary-gonadal axis (#176)

Spencer T Greatorex 1 2 , Daniel Bird 3 , David Reser 4 , Judy Ng 5 , Timothy J Cole 5
  1. Monash University, Clayton, VIC, Australia
  2. Biochemistry & Molecular Biology, Monash University, Clayton, Victoria, Australia
  3. Hudson Institute, Clayton, Victoria, 3168
  4. Physiology, Monash University, Clayton, Victoria, Australia
  5. Biochemistry & Molecular Biology, Monash University, Clayton, Victoria, Australia

The human Short-chain Dehydrogenase Reductase (SDR) superfamily of oxoreductase enzymes regulate important metabolic pathways involved in the biosynthesis of lipophillic endocrine hormones. The 11-beta hydroxysteroid dehydrogenase (11-betaHSD) enzymes have key roles in the pre-receptor modification of glucocorticoids, modifications that directly regulate blood pressure, fluid and electrolyte homeostasis, as well as modulating metabolic and brain function. Recently, a third member of the 11-betaHSD subfamily has been identified with a high level of protein sequence homology to 11βHSD1. Only two papers have investigated this enzyme in any detail and these studies suggested that 11βHSD1L was strongly expressed in the brain. Detailed information on the enzymology of 11β-HSD1L is unavailable with preliminary assays suggesting novel bidirectional interconversion of cortisol and cortisone interconversion and no activity towards 11-keto/hydroxy androgens. We have further characterised the gene ontology and expression patterns of 11βHSD1L using various Bioinformatic tools, real-time and droplet-digital qPCR and immunohistochemical analysis in the sheep, marmoset and macaque.

Conservation of two important enzyme catalytic domains was demonstrated through multiple sequence alignments and 3-dimensional homology modelling suggested significant levels of structural similarity between 11βHSD1L and 11βHSD1. mRNA expression analysis showed that HSD11B1L mRNA expression was highest in the ovary and pituitary, with moderate to low expression levels observed in other major organs, including the gut. Finally, immunofluorescence imaging of sheep/marmoset tissue showed strong protein localisation to granulosa cells of the ovary, gonadotrophs in the pituitary, and enteroendocrine cells in the small and large intestine. Intracellular localisation showed that 11βHSD1L was localised to the endoplasmic reticulum much like other cholesterol metabolising SDR family members including 11βHSD1. These results suggest that 11βHSD1L may play a role in reproduction through actions at various levels in the HPG-axis.