New method of extraction of intact nuclei from cells for flow cytometry fluorescence immunoassay

Abstract

Background. Identification of cellular proteins can be performed by indirect immunofluorescence assay using flow cytometry. However, this method allows to detect cellular proteins that are either on the cell surface or inside the cell and cannot demonstrate a protein distribution within cellular compartments, particularly in nucleus. Meanwhile, the nuclear localization of the protein of interest in many respects gives an indication of the mechanisms of its action. Therefore, the development of the protocol of extraction of nuclei suitable for analysis on a flow cytometer is able to complement the information about the localization and functional significance of many nucleus-associated proteins. Objective. The aim of this study was to develope a method for extraction, purification and stabilization of intact nuclei suitable for flow cytofluorimetry analysis. Materials and methods. In this work we studied the nuclear localization of the receptor type 1 for vascular endothelial growth factor (VEGF-R1). The A431 human cancer cell line was used as an object of the study. The quality of extracted nuclei was assessed by microscopic examination of stained smears of nuclear suspension. Expression of the receptor was determined by indirect immunofluorescence assay using flow cytometry. Results. New method was successfully applied to obtain the suspension of intact cellular nuclei that is crucial to perform further flow cytometry. Applied method revealed the presence of the receptor type 1 for vascular endothelial growth factor at the external nuclear membrane and inside of the nucleus. Interesting to note that the presence of the receptor type 1 for vascular endothelial growth factor inside ofthe nucleus was 3,8 times as much as its surface location (17,9 ± 1,04 % and 4,8 + 0,26 % respectively). Conclusions. The new method of extraction, purification and stabilization ofthe nuclei is applicable for proteins identification by flow cytometry. In combination with other methods (ICC, Western blotting, etc.) flow cytometry of intact nuclei is able to complement the information about the properties of nucleus-associated proteins.