A Fluorescence-based Protocol for Preliminary Screening of Protein Synthesis Inhibitors from Natural Sources

Summary

This protocol introduces a fluorometric screening methodology optimized for identifying natural product/small molecule inhibitors of protein synthesis. Its practicality makes it suitable for both undergraduate instruction in drug discovery techniques and implementation in medicinal chemistry campaigns.

Abstract

Natural products represent a rich source of therapeutic compounds with applications across multiple diseases, particularly cancer. By leveraging these biomolecules as structural templates in drug discovery, researchers have achieved both faster development timelines and improved biological effectiveness compared to fully synthetic compounds. The protein synthesis pathway has emerged as a compelling target for natural products, especially given its involvement in hard-to-treat cancers. The potent protein synthesis inhibitor cycloheximide, derived from Streptomyces griseus, exemplifies the potential of natural compounds in this space. As these natural product derivatives are developed into drug-like molecules, confirming their protein synthesis inhibitory activity remains a crucial validation step. The primary aim is to provide an undergraduate-friendly protocol for rapid evaluation of compound inhibition activity. The protocol employs a fluorescent substrate and advanced fluorescence microscopy techniques to systematically detect and measure the inhibitory capabilities of these natural products. The study examined compounds derived from two plant species: Pinus sylvestris and Psoralea corylifolia. Using cycloheximide as a reference inhibitor, both natural products showed varying levels of protein synthesis inhibition.

Introduction

Protein synthesis involves highly regulated processes: transcription and translation. During transcription, DNA sequences of genes are copied, producing messenger RNA (mRNA). The enzyme RNA polymerase works to separate the DNA double helix and uses one strand as a guide to build a matching mRNA molecule. Once the mRNA is fully formed, it travels from the nucleus out to the cytoplasm for translation. Translation occurs in the ribosome, wherein mRNA is used as a template to assemble amino acids into a polypeptide chain. This polypeptide chain, upon leaving the exit tunnel of the ribosome, is folded into a functional protein. Transcription is primarily regulated by trans....

Protocol

1. Reagent preparation from kit

NOTE: Adequately mix, spin down, and keep all reagents on ice until use.

1. Organize and obtain the protein synthesis inhibition kit, PBS buffer, cell culture medium, cell culture treated plates, 15 mL conical sterile polypropylene centrifuge tubes, 2 mL centrifuge tubes, p10, p20, p200, and p1000 pipettes, and appropriate tips.
2. Prepare wash buffer.
   1. Thaw the 10x wash buffer at 37 °C by cupping the vial in the hand. Use the body heat in the hands to thaw and frequently check if thawing is complete.
   2. Dilute the 10x wash buffer stocks 1:10 in deionized water in a cen....

Results

This assay utilized fluorescence to visualize and quantify different natural products' ability to inhibit protein synthesis. Cycloheximide (CHX) is a known protein synthesis inhibitor whose mode of action involves interfering with the translocation process during elongation¹¹. For this study, living cells were detected with a green, fluorescent nuclear dye. OPP is a derivative of puromycin that covalently binds to nascent proteins¹². The MDA-MB-231 cell line served as a.......

Discussion

This protocol provides a fluorometric screening methodology for testing natural products and small molecules to evaluate their ability to inhibit protein synthesis. The simplicity of this protocol enables undergraduate researchers to implement it correctly, allowing them to make substantive contributions to scientific knowledge. The protocol demands a basic comprehension of biological methods and techniques, with steps requiring careful execution to ensure accurate and reliable results.

For in.......

Materials

List of materials used in this article

Name	Company	Catalog Number	Comments
Agilent Biotek Cytation 1 Cell Imaging Multi-Mode Reader	Agilent	BTCYT1V
Compound 1 (Dehydroabietylamine, CAS 1446-61-3)	Enamine	EN300-7409771
Compound 2 (Bakuchiol, CAS 10309-37-2)	ChemFaces	CFN99047
Heraeus Megafuge 16R	Thermo Scientific	75004271
Ibidi Gmbh-slide 96-well plate	Ibidi	80826
MDA-MB-231 Cell Lines	ATCC	ATCC HTB-26
Phosphate Buffered Saline pH 7.4	ATCC	ATCC 30-2200
Protein Synthesis Assay Kit (Green)	Abcam	Ab239725