Humpath.com - Human pathology

Home > B. Cellular pathology > Golgi apparatus

Golgi apparatus

Monday 9 June 2003

Definition: Cellular organelle responsible for glycosylation, and protein- and membrane-sorting in mammalian cells.

Golgi Bodies can be considered the final packaging location for proteins and lipids. Each Golgi body consists of flattened membrane sacs. It is within the flattened membrane sacs that enzymes ready these proteins and lipids for shipment to specific locations.

Vesicles form at the final region of a Golgi body when parts of the membrane begin to bulge. These vesicles then break away, via exocytosis, for the transport of these proteins and lipids to their final destination.

Within the Golgi body (or Golgi apparatus), these proteins and lipids are labeled with sequences of molecules (an address) which tell the body where these products should be delivered.

In eukaryotic cells, the Golgi apparatus receives newly synthesized proteins from the endoplasmic reticulum (ER) and delivers them, after covalent modification, to their destination in the cell.

These proteins move from the inside (cis) face of the Golgi to the plasma-membrane (trans) side, through a stack of cisternae, towards the trans-Golgi network (TGN).

- SNAREs

The specificity of membrane transport reactions is thought to be determined by correct pairing of vesicle-associated SNAREs (v-SNAREs) with those on the target membrane (t-SNAREs). This complex then recruits soluble NSF attachment proteins (SNAPs) and N-ethylmaleimide-sensitive factor (NSF)(MIM.601633) to form a 20S SNARE complex.

- Golgi subcompartmentalization

The subcompartmentalized structure of the Golgi apparatus contributes to efficient glycosylation in the secretory pathway. Subcompartmentalization driven by maturation relies primarily on constant and accurate vesicle-mediated local recycling of Golgi residents.

The precision of this vesicle transport is dependent on the interplay between the key factors that mediate vesicle budding and fusion—the coat proteins and the SNARE fusion machinery. These alone, however, may not be sufficient to ensure establishment of compartments de novo, and additional regulatory mechanisms operate to modify their activity.

- The Golgi apparatus is a stack of compartments that serves as a central junction for membrane traffic, with carriers moving through the stack as well as arriving from, and departing toward, many other destinations in the cell. This requires that the different compartments in the Golgi recruit from the cytosol a distinct set of proteins to mediate accurate membrane traffic.

This recruitment appears to reflect recognition of small GTPases of the Rab and Arf family, or of lipid species such as PtdIns(4)P and diacylglycerol, which provide a unique "identity" for each compartment.

Trans-Golgi network (TGN)

The composition and identity of cell organelles are dictated by the flux of lipids and proteins that they receive and lose through cytosolic exchange and membrane trafficking.

The trans-Golgi network (TGN) is a major sorting centre for cell lipids and proteins at the crossroads of the endocytic and exocytic pathways; it has a complex dynamic structure composed of a network of tubular membranes that generate pleiomorphic carriers targeted to different destinations.

See also

- Golgi-resident proteins

Video

- protein glycosylation in the Golgi apparatus

@<@object width="425" height="350">@<@param name="movie" value="http://www.youtube.com/v/G33cD2YleRI">@<@/param>@<@param name="wmode" value="transparent">@<@/param>@<@embed src="http://www.youtube.com/v/G33cD2YleRI" type="application/x-shockwave-flash" wmode="transparent" width="425" height="350">@<@/embed>@<@/object>

References

- De Matteis MA, Luini A. Exiting the Golgi complex. Nat Rev Mol Cell Biol. 2008 Apr;9(4):273-84. PMID: 18354421

- Puthenveedu MA, Linstedt AD. Subcompartmentalizing the Golgi apparatus. Curr Opin Cell Biol. 2005 Aug;17(4):369-75. PMID: 15975779

- Munro S. The Golgi apparatus: defining the identity of Golgi membranes. Curr Opin Cell Biol. 2005 Aug;17(4):395-401. PMID: 15975778

- Barr FA. The Golgi apparatus: going round in circles?
Trends Cell Biol. 2002 Mar;12(3):101-4. PMID: 11859015

- Storrie B, Pepperkok R, Nilsson T. Breaking the COPI monopoly on Golgi recycling. Trends Cell Biol. 2000 Sep;10(9):385-91. PMID: 10932096