GPR55 and N-acyl Amino Acids

<p>G-protein coupled receptor 55 (GPR55) is a novel lipid sensing receptor activated by the endogenous lipid, lysophosphatidylinositol (LPI) and is reported as a putative cannabinoid receptor. However GPR55 shares limited homology with the two cloned cannabinoid receptors (CB₁ and CB₂) but does exhibit some cannabinoid sensitivity. Recently a family of bioactive lipids, the N-acyl amino acids, are gaining interest due to their structural similarity to endocannabinoids (naturally occurring CB₁ and CB₂ agonists). N-acyl amino acids have little or no affinity for either CB₁ or CB₂ and many have no known biological target at present.</p> <p>This study used a subset of N-acyl amino acids; possessing either a serine or glycine head group attached to varying fatty acid chains; to assess these novel lipids as potential GPR55 ligands. Three cell lines were utilised, a stably transfected HEK293 cell line that overexpresses 3xHA N-terminus tagged hGPR55 (hGPR55-HEK293 cells) and control HEK293 cells. In addition, the DU145 a prostate cancer cell line which is reported to endogenously express GPR55 was investigated. N-acyl amino acid challenge activated GPR55 to promote Ca²⁺ mobilisation, CREB phosphorylation, actin cytoskeletal reorganisation and elongation of focal adhesions. Furthermore GPR55-mediated downstream signalling effectors were studied comparing LPI to the orphan lipid; N oleoyl-L-serine (NOSer).</p> <p>This study highlights that N-acyl amino acids act as GPR55 agonist/partial agonists in hGPR55-HEK293 cells. Both LPI and NOSer exert effects in prostate cancer cells (DU145s) which are GPR55 mediated. GPR55 may exhibit ligand bias as LPI was more efficacious in Ca²⁺ mobilisation. However in the pCREB assay NOSer was more efficacious than LPI. A similar efficacy and potency to either LPI or NOSer was observed in the other assays in both hGPR55-HEK293 and DU145 cells. Furthermore this study is the first where a named GPCR can be assigned for responses that are mediated by NOSer.</p>

Name dc:type.qualificationname

Doctor of Philosophy

Level dc:type.qualificationlevel

Doctoral Thesis

Grantor dc:publisher.institution

University of Dundee

Year dc:date.issued

2013

Author dc:creator

• Penman, June

Language dc:language

eng

Identifier

oai:discovery.dundee.ac.uk:studenttheses/2e07c280-3a61-4f49-a9da-1fa4ffc79fa5

OAI identifier oai:identifier

oai:discovery.dundee.ac.uk:studenttheses/2e07c280-3a61-4f49-a9da-1fa4ffc79fa5