Journal club today

Gown presented about a paper from Davis, G. lab.
K.Poskanzner, G.Davis et al. "Synaptotagmin I is necessary for compensatory synaptic vesicle endocytosis in vivo" Nature \ 426, 559 - 563
They introduce synaptotagmin-I with FLaSh (fluorescein-like fluorophore that binds tetra-cystein domain) into synaptotamin-null fly, and photo-inactivate synaptotagmin-I. Endocytosis was monitored by n-Synaptobrevin with pH-sensitive GFP. shibire mutation which blocks endocytosis temperature dependently was used to trap vesicles at plasma membrane. Inactivation of synaptotagmin caused block of endocytosis. Thus synaptotagmin is a part of endocytosis machinery.
Discussion points: photo-inactivation depends on the production of free-radical from the excited fluorophore. Thus, the inactivation should not be so spacific. For example it could kill whole endocytotic machinery. Their previous paper showed that osmolarity-induced transmitter release is intact after the photo-inactivation as a control. However, because the release mechanism is completely different, this is not really a good control.