TaqManR Proximity ligation technology for the detection of heterodimeric adhesion receptors on lymphocytes

TaqManR proximity ligation technology (TaqManR PLA) is an innovative advancement of immuno PCR. It allows a fast and quantitative detection of vicinal proteins or protein–protein interactions from cell lysates by combining antibody–antigen binding with a real-time PCR detection. We tested if TaqManR PLA also was applicable to investigate and relatively quantitate adhesion receptor heterodimers such as the alpha-4/beta-1 integrin on the surface of intact cells.Both, alpha-4, beta-1 and the alpha-4/beta-1 heterodimer were detected on the surface of lymphocytes by TaqManR PLA. Results were specific, reproducible and comparable to flow cytometric data. However, preciseness of reactions varied dependent on the antibody pairs used. Co-detection of proximate identical subunits suggested clusters of alpha-4 and/or beta-1 on the cell surface which we confirmed by microscopy.We conclude that real-time PCR-based TaqManR PLA is of limited applicability to investigate heterodimeric receptor molecules such as the alpha-4/beta-1 integrin. Determination of an abundance ratio of alpha-4/beta-1 in relation to total alpha-4 or beta-1 was not possible and real-time detection did not allow conclusions on the surface distribution of molecules. The related in situ PLA developed for microscopy allows visualizing proximate protein interactions and might be an interesting alternative for research into receptor heterodimers and their surface distribution on immune cells.