Since 2001, Prof. Dr. Rizzoli focused his work on mechanisms of pre-synaptic function, especially on synaptic vesicle recycling. Over the years, we have identified and developed a new concept of neurotransmitter release, in which a small number of “perfect” synaptic vesicles participate in most synaptic release events. These vesicles are mobile and therefore are always able to move towards the release sites (active zones), while all other vesicles are immobile, and fuse only rarely. We have described various elements of this model (Rizzoli and Betz, Science, 2004; Westphal et al., Science, 2008; Kamin et al., Biophys J, 2010; Hoopmann et al., PNAS, 2010; Wilhelm et al., Nat Neurosci, 2010), and also extended it to most known synaptic preparations in important reviews of the field (Rizzoli and Betz, Nat Rev Neurosci, 2005; updated in Denker and Rizzoli, Front Synaptic Neurosci, 2010). Recently, we demonstrated this concept in synapses of behaving animals, in what is the first study of vesicle function in vivo (Denker et al., PNAS, 2011a; Denker et al., PNAS, 2011b). In addition to the synaptic vesicle studies, I have applied the membrane trafficking tools I developed to other systems such as endosomal sorting (for example Bethani et al., EMBO J, 2007; Barysch et al., PNAS, 2009).
In a second perspective, we have a strong interest in developing microscopy techniques, most importantly by applying super-resolution microscopy to biological questions. Focusing on stimulated emission depletion (STED) microscopy, we provided the first true biological application of the technique (Willig et al., Nature, 2006) and the first live-imaging application (Westphal et al., Science, 2008), besides participating in other efforts such as the first multi-color super-resolution applications (Donnert et al., Biophys J, 2007).