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The 39th Harden Conference sponsored by The Biochemical Society heldon Sept 20-25, 1992 at Wye College, Ashford, Kent, UK focused discussions on the components involved in the various steps of intracellular transport. The talk on the eukaryotic secretory pathway provided the most stimulating and thought-provoking discussion. The topics discussed included protein folding, endoplasmic reticulum (ER)-retention and recycling, ER-Golgi transport, trimeric G-proteins, small GTP-binding proteins and exocytosis.

Transport vesicles require the presence of specific membrane proteins toidentify their destination. One model assumes that the transport vesicle carries the identifying tag, which interacts with a target organelle through membrane fusion. A protein that had been known to play a part in membrane fusion events has been identified. NSF and its attachment proteins (SNAPs) have been used to determine the presence of SNAP receptors, syntaxins A and B and synaptobrevin.

The disappearance of the Golgi complex under conditions such as mitosis and in cells treated with brefeldin A is being studied through a combined approach that involves molecular genetics, cytology and research on intra-cellular transport. Golgi disassembly is also being studied in cells undergoing secretion defective, temperature-sensitive mutations. Recent research findings indicate that Golgi disappearance is related to overexpression of the homologue of the ERD-2 ER salvage receptor and a related protein called ELP-1, in humans.

The retention of golgi-resident proteins is facilitated by their transmembrane domain. Levels of protein expresssion determines retention efficiency. Studies on the cis Golgi protein, E1, and trans Golgi-resident proteins - galactosyl transferase and sialyl transferase support this hypothesis. Two possible mechanisms are proposed. First, the transmembrane domains of different resident proteins interact to spontaneously form a meshwork leading to retention. Second, an integral protein of the lipid bilayer binds and translocates proteins specifically.