Structure-activity study of LVV-hemorphin-7: angiotensin AT4 receptor ligand and inhibitor of insulin-regulated aminopeptidase.
The decapeptide LVV-hemorphin-7 binds with high affinity to the angiotensin IV (Ang IV) receptor (AT(4) receptor), eliciting a number of physiological effects, including cellular proliferation and memory enhancement. We have recently shown that the AT(4) receptor is identical to insulin-regulated aminopeptidase (IRAP) and that both LVV-hemorphin-7 and Ang IV inhibit the catalytic activity of IRAP. In the current study, a series of alanine-substituted and N- or C-terminally modified analogs of LVV-hemorphin-7 were evaluated for their abilities to compete for (125)I-Ang IV binding in sheep adrenal and cerebellar membranes. Selected analogs were also analyzed for binding to recombinant human IRAP and inhibition of IRAP aminopeptidase activity. C-Terminal deletions of LVV-hemorphin-7 resulted in modest changes in affinity for IRAP, whereas deletion of the first three N-terminal residues abolished binding. Monosubstitutions of Tyr(4) and Trp(6) with alanine resulted in a 10-fold reduction in affinity. Competition binding studies using recombinant human IRAP demonstrated the same rank order of affinity as obtained for the ovine tissues. All LVV-hemorphin-7 analogs tested, except for Leu-Val-Val-Tyr, inhibit the cleavage of the synthetic substrate, leucine beta-naphthylamide, by IRAP, with K(i) values between 56 and 620 nM. We find that the Val(3) residue is crucial for LVV-hemorphin-7 binding to IRAP, whereas the C-terminal domain seems to play a minor role. The current study highlights the minimal residues necessary for binding and inhibition of IRAP and provides a basis to design peptidomimetic analogs for experimental and potentially clinical use.
Lee
Joohyung
J
Howard Florey Institute, University of Melbourne, Parkville, Victoria, Australia.
Mustafa
Tomris
T
McDowall
Sharon G
SG
Mendelsohn
Frederick A O
FA
Brennan
Michelle
M
Lew
Rebecca A
RA
Albiston
Anthony L
AL
Chai
Siew Yeen
SY
D000409:Alanine / Q000235:genetics / Q000378:metabolism; D020816:Amino Acid Motifs; D019943:Amino Acid Substitution; D000626:Aminopeptidases / Q000378:metabolism*; D057911:Angiotensin Receptor Antagonists; D002478:Cells, Cultured; D004347:Drug Interactions; D017353:Gene Deletion; D006454:Hemoglobins / Q000737:chemistry / Q000235:genetics / Q000494:pharmacology*; D006801:Humans; D007328:Insulin / Q000494:pharmacology; D053590:Interleukin 1 Receptor Antagonist Protein; D008024:Ligands; D010446:Peptide Fragments / Q000737:chemistry / Q000235:genetics / Q000494:pharmacology*; D010455:Peptides / Q000494:pharmacology; D011945:Receptors, Angiotensin; D011994:Recombinant Proteins / Q000378:metabolism; D012795:Sialoglycoproteins / Q000378:metabolism; D013329:Structure-Activity Relationship
C090830:AT4 receptor; D057911:Angiotensin Receptor Antagonists; D006454:Hemoglobins; C507763:IL1RN protein, human; D007328:Insulin; D053590:Interleukin 1 Receptor Antagonist Protein; D008024:Ligands; D010446:Peptide Fragments; D010455:Peptides; D011945:Receptors, Angiotensin; D011994:Recombinant Proteins; D012795:Sialoglycoproteins; C074309:LVV-hemorphin-7; D000626:Aminopeptidases; D000409:Alanine