Activity-based fluorescent reporters for monoamine oxidases in living cells

Abstract

Monoamine Oxidase Reporters 1 and 2 (MR1 and MR2) are substrate-tethered activity probes that utilize a tandem amine oxidation/beta-elimination mechanism to detect MAO chemistry in vitro and in living cells directly and specifically without the need for additional enzymes or other activating reagents.

A sensitive two-photon probe to selectively detect monoamine oxidase B activity in Parkinson’s disease models

“…1c as the fluorogenic reporters due to their different molecular sizes and excellent properties in live-cell/tissue imaging 29,34 . We further introduced N-monomethylation and N,N-dimethylation to the propylamine group, as alkylated states of propylamine were previously shown to respond differentially to MAOs [17][18][19][20] . In total, nine probes, including the acedan-based (U1/2/3; Fig.…”

“…Of the various types of standard assays employed to detect MAO activities [14][15][16][17][18][19][20][21][22] , advanced fluorescence-based methods might be suitable in this context 23 , owing to their practicality, high sensitivity and amenability to deep-tissue bioimaging (that is, by using nearinfrared 24 or two-photon techniques 25 ); however, few provide any MAO-A/B selectivity 22 . For example, the commercially available Amplex Red kit and ELISA kit (ab109912), as well as several other existing fluorimetric approaches [14][15][16] , measures the fluorescent product liberated from the oxidation of the corresponding amine substrate by MAOs, in many cases with the assistance of a secondary enzyme or activating reagent (for example, NaIO 4 ).…”

“…For example, the commercially available Amplex Red kit and ELISA kit (ab109912), as well as several other existing fluorimetric approaches [14][15][16] , measures the fluorescent product liberated from the oxidation of the corresponding amine substrate by MAOs, in many cases with the assistance of a secondary enzyme or activating reagent (for example, NaIO 4 ). Chang and co-workers 19 reported a small molecule resorufin-based probe capable of live-cell imaging of MAO activities. Other studies based on similar design principles but with different fluorogenic MAO substrates have also been reported 18,20 .…”

Evaluation of the oxidation of 1-methyl-4-phenyl-1,2,3,6-tetrahydropyridine (MPTP) to toxic pyridinium cations by monoamine oxidase (MAO) enzymes and its use to search for new MAO inhibitors and protective agents

“…Therefore, studying MAO enzymes and finding new MAO inhibitors as purported neuroprotectants is a subject of current interest in drug discovery 1,[18][19][20][21][22][23][24][25][26] . MAO enzymes are usually monitored by measuring the absorbance and/or fluorescence of the oxidation products generated from key amines (kynuramine, tryptamine, tyramine, etc) [27][28][29][30][31][32][33] . The purpose of this research was to evaluate the oxidation of the neurotoxin MPTP by human MAO isozymes (human MAO-A and B) through the chromatographic analysis of the toxic pyridinium species (MPDP + and MPP + ) generated, and subsequently use this approach as a new tool to search for new MAO inhibitors (MAO-A and B) and eventual protective agents.…”

Fluorescent Probes for Analysis and Imaging of Monoamine Oxidase Activity

“…27 It is known that fluorophores such as resorufin, fluoresceins, and 7-hydroxycoumarns give turn-on type fluorescence change when the hydroxyl group in its ether form undergoes deprotection to the free hydroxyl group. Other related fluorescent probes have been developed based on this sensing strategy.…”