Cell biology of protein glycosylation: a celebration of the career of Jürgen Roth on the occasion of his 70th birthday

Abstract

Professor Jurgen Roth, a pioneer in post-embedding labelling methodology at the electronmicroscopic level, has had a long and distinguished career studying the cell biology of protein glycosylation, resulting in the publication of more than 300 original manuscripts, over 30 review articles, 37 book chapters and 4–5 books. On the occasion of his 70th birthday, I would like to pay tribute by highlighting his most august accomplishments and contributions to this area of cell biology. Early in his investigations it became necessary to develop new staining probes and tissue processing methods for imaging glycosylation reactions at the subcellular level. Accordingly, in the 1970s he published a series of methods using a variety of lectins and electron dense markers for the histochemical detection of glycoconjugates at the electron microscopic level (Roth et al., 1972, 1974, 1975; Roth and Thoss, 1974; Roth and Franz, 1975; Roth and Wagner, 1977; Roth and Binder, 1978). He was then invited by Professor Lelio Orci to relocate from his native Germany to Geneva, Switzerland and introduce to Orci’s lab the techniques of immunoferritin and colloidal gold at the electron microscopic level. Shortly after his arrival in Geneva, Roth et al. (1978) published a seminal technical paper in immunoelectron microscopy (Figure 1), introducing the protein A–gold technique for post-embedding immunoelectron microscopic localization of tissue antigens. The introduction of the protein A–gold complex by Roth for immunolabelling revolutionized intracellular antigen localization by providing a high-resolution, high-electron dense marker far superior to the then available markers, such as peroxidase and ferritin. Moreover, the affinity of protein A for the Fc region of immunoglobulins provided a versatile, general second-step reagent for many immunocytochemical techniques, quickly establishing this method as literally the “gold standard” for immunoelectron microscopy. The original manuscript used glutaraldehyde-fixed, conventionally dehydrated and epoxy-embedded samples for the postembedding demonstration of robust pancreatic enzymes. Unfortunately, many antigens do not survive the harsh processing steps employed in conventional electron microscopy. At the time, however, a most fortunate collaboration arose when Roth was invited to visit Professor Eduard Kellenberger’s group at the Biocenter at the University of Basel. They were developing low-temperature hydrophilic resins for electron microscopy, and the two groups together demonstrated the superiority of these resins (Lowicryl resins) in conjunction with low temperature dehydration and embedding for antigen retention and morphological preservation for post-embedding immunoelectron microscopy (Roth et al., 1981a) (Figure 2). In this same manuscript, they also demonstrated the efficacy of using the readily identifiable