title: Identification of critical residues within the conserved and specificity patches of nerve growth factor leading to survival or differentiation.
abstract: Afflicted neurons in Alzheimer disease have been shown to display an imbalance in the expression of TrkA and p75(NTR) at the cell surface, and administration of nerve growth factor (NGF) has been considered and attempted for treatment. However, wild-type NGF causes extensive elaboration of neurites while providing survival support. This study was aimed at developing recombinant NGF muteins that did not support neuritogenesis while maintaining the survival response. Critical residues were identified at the ligand-receptor interface by point mutagenesis that played a greater importance in neuritogenesis versus survival. By combining point mutations, two survival-selective recombinant NGF muteins, i.e./7-84-103 and KKE/7-84-103, were generated. Both muteins reduced neuritogenesis in PC12 (TrkA(+)/p75(NTR+)) cells by >90%, while concurrently retaining near wild-type survival activity in MG139 (TrkA(+) only) and PCNA fibroblast (p75(NTR+)-only) cells. Additionally, survival in both naive and terminally differentiated PC12 cells was shown to be intermediate between NGF and negative controls. Dose-response curves with 7-84-103 showed that the differentiation curve was shifted by about 100-fold, whereas the EC(50) for survival was only increased by 3.3-fold. Surface plasmon resonance analysis revealed a 200-fold decrease in binding of 7-84-103 to TrkA. The retention of cell survival was attributed to maintenance of signaling through the Akt survival pathway with reduced MAPK signaling for differentiation. The effect of key mutations along the NGF receptor interface are transmitted inside the cell to enable the generation of survival-selective recombinant NGF muteins that may represent novel pharmacologic lead agents for the amelioration of Alzheimer disease.
authors.affiliation: Department of Biochemistry and Molecular Biology, Chicago Medical School, Rosalind Franklin University of Medicine and Science, North Chicago, Illinois 60064, USA.
authors.forename: Sidharth
authors.initials: S
authors.lastname: Mahapatra
authors.forename: Hrishikesh
authors.initials: H
authors.lastname: Mehta
authors.forename: Sang B
authors.initials: SB
authors.lastname: Woo
authors.forename: Kenneth E
authors.initials: KE
authors.lastname: Neet
mesh_terms: D000595:Amino Acid Sequence; D000596:Amino Acids / Q000737:chemistry / Q000235:genetics / Q000378:metabolism; D000818:Animals; D001665:Binding Sites / Q000235:genetics; D002454:Cell Differentiation / Q000187:drug effects / Q000502:physiology*; D002460:Cell Line; D002470:Cell Survival / Q000187:drug effects / Q000502:physiology; D004305:Dose-Response Relationship, Drug; D005347:Fibroblasts / Q000166:cytology / Q000187:drug effects / Q000378:metabolism; D020935:MAP Kinase Signaling System; D008958:Models, Molecular; D016297:Mutagenesis, Site-Directed; D050505:Mutant Proteins / Q000737:chemistry / Q000378:metabolism / Q000494:pharmacology; D020932:Nerve Growth Factor / Q000235:genetics / Q000378:metabolism* / Q000494:pharmacology; D016501:Neurites / Q000187:drug effects / Q000502:physiology; D016716:PC12 Cells; D011485:Protein Binding; D017434:Protein Structure, Tertiary; D051381:Rats; D020800:Receptor, Nerve Growth Factor / Q000737:chemistry / Q000378:metabolism*; D020917:Receptor, trkA / Q000737:chemistry / Q000378:metabolism*; D011994:Recombinant Proteins / Q000737:chemistry / Q000378:metabolism / Q000494:pharmacology; D018411:Spodoptera; D020349:Surface Plasmon Resonance
chemical_list: D000596:Amino Acids; D050505:Mutant Proteins; D020800:Receptor, Nerve Growth Factor; D011994:Recombinant Proteins; D020932:Nerve Growth Factor; D020917:Receptor, trkA