Robust Comparison of Protein Levels Across Tissues and Throughout Development Using Standardized Quantitative Western Blotting

Summary

This method describes a robust and reproducible approach for the comparison of protein levels in different tissues and at different developmental timepoints using a standardized quantitative western blotting approach.

Abstract

Western blotting is a technique that is commonly used to detect and quantify protein expression. Over the years, this technique has led to many advances in both basic and clinical research. However, as with many similar experimental techniques, the outcome of Western blot analyses is easily influenced by choices made in the design and execution of the experiment. Specific housekeeping proteins have traditionally been used to normalize protein levels for quantification, however, these have a number of limitations and have therefore been increasingly criticized over the past few years. Here, we describe a detailed protocol that we have developed to allow us to undertake complex comparisons of protein expression variation across different tissues, mouse models (including disease models), and developmental timepoints. By using a fluorescent total protein stain and introducing the use of an internal loading standard, it is possible to overcome existing limitations in the number of samples that can be compared within experiments and systematically compare protein levels across a range of experimental conditions. This approach expands the use of traditional western blot techniques, thereby allowing researchers to better explore protein expression across different tissues and samples.

Introduction

Western blotting is a technique that is commonly used to detect and quantify protein expression, including in tissue homogenates or extracts. Over the years, this technique has led to many advances in both basic and clinical research, where it can be used as a diagnostic tool to identify the presence of disease^1,2. Western blotting was first described in 1979 as a method to transfer proteins from polyacrylamide gels to nitrocellulose sheets and subsequently visualize proteins using secondary antibodies that were either radioactively labelled or conjugated to fluorescein or peroxidase³. ....

Protocol

Tissues for this procedure were obtained from animal studies that were approved by the internal ethics committee at the University of Edinburgh and were performed in concordance with institutional and UK Home Office regulations under the authority of relevant personal and project licenses.

NOTE: This protocol has been optimized using standardized, commercially available kits and reagents in order to increase reproducibility (see Table of Materials).

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Discussion

With the appropriate experimental design, control measures and statistical analysis, western blotting can be used to make reliable quantitative estimates of protein expression within and between a varied range of biological samples. The protocol we describe in the current manuscript aims to serve as a guideline for researchers looking to use Western blotting to undertake quantitative analysis across larger and more complex groups of samples, by using a combination of fluorescence-based detection methods, total protein lo.......

Materials

Name	Company	Catalog Number	Comments
Fine Tipped Gel Loading Tips	Alpha Laboratories	GL20057SNTL
Halt Protease Inhibitor Cocktail, EDTA-free 100x 5mL	ThermoFisher Scientific	78437
Handheld homogeniser	VWR Collection	431-0100
iBlot 2 Gel Transfer Device	ThermoFisher Scientific	IB21001
iBlot Transfer Stack, PVDF, regular size	ThermoFisher Scientific	IB401031
Image Studio Lite	Licor	N/A	Free download from https://www.licor.com/bio/products/software/image_studio_lite/
IRDye 800CW secondary antibodies	Licor	--	Select appropriate secondary antibody that is specific against host of primary antibody.
Micro BCA Protein Assay Kit	ThermoFisher Scientific	23235
Novex Sharp Pre-stained Protein Standard	ThermoFisher Scientific	LC5800
NuPAGE 4-12% Bis-Tris Protein Gels, 1.0 mm, 15-well	ThermoFisher Scientific	NP0323BOX
NuPAGE LDS Sample Buffer (4X)	ThermoFisher Scientific	NP0007
NuPAGE MOPS SDS Running Buffer (20X)	ThermoFisher Scientific	NP0001
Odyssey Blocking Buffer	Licor	927-40000
Purified Mouse anti-SMN (survival motor neuron) monoclonal antibody	BD Transduction Laboratories	610646	Is used extensively in the SMN/SMA literature and gives consistent results regardsless of lot number
REVERT Total Protein Stain, 250 mL	Licor	926-11021
REVERT Wash Solution	Licor	926-11012
RIPA Lysis and Extraction Buffer	ThermoFisher Scientific	89900
XCell SureLock Mini-Cell	ThermoFisher Scientific	EI0001