Membrane fusion is an essential step during the trafficking of endosomes and vesicles throughout the cell. Membrane fusion events are facilitated by multisubunit tethering complexes (MTC) including CORVET and HOPS. These complexes interact with Rab GTPases and SNARE proteins to promote the fusion of endosomes and lysosomes (1). In yeast VPS41 is a component of the HOPS complex that is needed for transport of endosomes and Golgi-derived vesicles to the vacuole. The choice between these two substrates is facilitated by the phosphorylation of VPS1 by Yck3 (2). Carbrera et al.
Caspases are a family of cysteine-aspartic acid proteases that are responsible for the initiation and execution of apoptosis. Caspase-8 is a 55 kDa protein expressed as an inactive procaspase that resides in the cytosol. Activation of Caspase-8 requires cleavage into its large (17-21 kDa) and small (10-13 kDa) catalytic subunits. Caspase-8 has been shown to play a role in the induction of apoptosis by both death receptor mediated and non-receptor mediated mechanisms (1). Caspase-8 signals to effector Caspase-3 to execute apoptosis.
Programmed cell death via apoptosis is a key controlled physiological process instigated by the cell death receptor family, their ligands, and the caspase cysteine protease family. All caspases exist in a precursor form that contains a prodomain, and large and small catalytic subunits. A cleavage event adjacent to an aspartate liberates one large and one small subunit, which are now free to associate into an active a2b2 tetramer. Caspases are activated by triggers such as ligand-receptor interactions, growth factor deprivation, and cell function inhibitors.
