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                                             BIOINFORMATICS COLLOQUIUM
						College of Science
                                              George Mason University
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				        The Golgi complex in life and death
						 
                                               Carolyn Machamer, Ph.D.

				                     Cell Biology
                                    Johns Hopkins University School of Medicine                                                        
                                            725 N. Wolfe Street, 105 WBSB
                                                 Baltimore, MD 21205 

Abstract:
The Golgi complex is a ubiquitous eukaryotic organelle, involved in processing and sorting of cargo in 
the cellular secretory pathway. The structure of the organelle in mammalian cells is elaborate, comprised 
of many sets of stacked cisternal membranes held near the nucleus in a ribbon-type structure. The reason 
for this elaborate organization is a mystery, since in lower eukaryotic cells, a much simpler structure 
performs efficient processing and sorting of cargo. One idea is that the mammalian Golgi structure has 
evolved to perform an additional function as a signaling platform for transducing stress signals from the 
secretory pathway to the rest of the cell.

Golgins are peripheral Golgi membrane proteins that are thought to play a role in Golgi structure and 
function. Some of these proteins are phosphorylated during mitosis, which contributes to reversible 
disassembly of the Golgi complex during cell division. In addition, some golgins are cleaved during 
apoptosis (programmed cell death), leading to irreversible Golgi disassembly. Our work with golgin-160 
will be presented. Golgin-160 is involved in trafficking of specific cargo molecules, and is phosphorylated 
during mitosis. It is also an early target for cleavage by caspases during apoptosis. Expression of a 
caspase-resistant version of golgin-160 blocks apoptosis caused by a subset of pro-apoptotic stimuli, 
suggesting that cleavage of golgin-160 may be involved in transducing some apoptotic signals. We are 
exploring the possibility that some fragments of golgin-160 (which enter the nucleus after cleavage) 
promote gene expression that regulates the cellular response to stress.