Two types of exocytosis are known, full fusion and transient fusion, first type is dominant form in melanotrophs, which are therefore appropriate cell type for measurements of bulk exocytosis. Sfingolipid sphingosine recruits protein VAMP2 for SNARE complex formation, which is important for membrane fusion. We discovered that sphingosine and its structure homologue fingolimod increased exocytosis, if added extracellularly. We also studied exocytosis in lactotrophs, where transient fusion is dominant mode of exocytosis. We measure exocytosis by monitoring discrete steps in membrane capacitance, which is proportional to the changes in surface area of plasma membrane. In the presence of sphingosine the frequency of transient and full-fusion events increased. Vesi cles with larger diameters proceeded to full fusion, while smaller vesicles remained entrapped in transient exocytosis. Labeling with fluorescent antibodies recognizing prolactin (PRL) showed that the average diameter of secreted, but undegradated vesicle content was larger than diameter of unsecreted vesicles. PRL- and VAMP2-antibodies revealed that the intensity of VAMP2 signal was independent of PRL vesicle diameter. However, the density of VAMP2 signals was reduced in larger vesicles. We propose that sphingosine-mediated facilitation of regulated exocytosis is not only related to the number of SNARE complexes per vesicle but also depends on the vesicle size, which may determine the transition between transient and full-fusion exocytosis.
D.09 Tutoring for postgraduate students
COBISS.SI-ID: 784247Super resolution microscopy is the cutting edge technology with the resolution that is at list twice better than the resolution of conventional far field microscopy. One of the key instuments of super resolution microscopy is STED technology based instrument, which is now located also in Slovenia. It represents the most advanced technology in the field of optical microscopy, comprised of most advanced optics, mechanics and electronics. It enables observation of living objects at resolution between 35 and 40 nm with the potential to visualize objects beyond these limits. The conference with a workshop of the demonstration of the super-resolution microscopy is dedicated to the introduction of this technological novelty.
B.01 Organiser of a scientific meeting
COBISS.SI-ID: 2814543