Changes

===What types of secretion are controlled by the Golgi complex?===

===What types of secretion are controlled by the Golgi complex?===

The Golgi complex controls trafficking of different types of proteins. Some are destined for secretion. Others are destined for the extracellular matrix. Finally, other proteins, such as lysosomal enzymes, may need to be sorted and sequestered from the remaining constituents because of their potential destructive effects. This figure shows the two types of secretory pathways. The regulated secretory pathway, as its name implies, is a pathway for proteins that requires a stimulus or trigger to elicit secretion. Some stimuli regulate synthesis of the protein as well as its release. The constitutive pathway allows for secretion of proteins that are needed outside the cell, like in the extracellular matrix. It does not require stimuli, although growth factors may enhance the process.

The Golgi complex controls trafficking of different types of proteins. Some are destined for secretion. Others are destined for the extracellular matrix. Finally, other proteins, such as [[lysosomal enzymes]], may need to be sorted and sequestered from the remaining constituents because of their potential destructive effects. This figure shows the two types of secretory pathways. The regulated secretory pathway, as its name implies, is a pathway for proteins that requires a stimulus or trigger to elicit secretion. Some stimuli regulate synthesis of the protein as well as its release. The constitutive pathway allows for secretion of proteins that are needed outside the cell, like in the extracellular matrix. It does not require stimuli, although growth factors may enhance the process.

===Golgi complex regulation of insertion of plasma membrane proteins===

===Golgi complex regulation of insertion of plasma membrane proteins===

There is much interest in understanding how the different Golgi cisternae are organized and differentiated. A number of models exist, however a favorite is called the "Maturational model" <ref>Bannykh S.I. and Bakch, W.E. Membrane Dynamics at the Endoplasmic Reticulum Golgi Interface J Cell Biol 138: 1-4 1997)</ref>

There is much interest in understanding how the different Golgi cisternae are organized and differentiated. A number of models exist, however a favorite is called the "Maturational model" <ref>Bannykh S.I. and Bakch, W.E. Membrane Dynamics at the Endoplasmic Reticulum Golgi Interface J Cell Biol 138: 1-4 1997)</ref>

The Maturational model suggests that the new vesicles from the ER enter the cis Golgi network and retrograde vesicles (bearing COPI) coats move to merge with the cis region cisternae.  These carry Golgi complex processing enzymes and their targeting to this region may be dependent on the low concentration of these processing enzymes.  Then, as processing continues, the middle cisternae contain more mature product and lower amounts of the enzymes needed in the beginning.  Finally, the trans region is specialized for sorting, containing receptors to sort and isolate lysosomal enzymes, for example.<ref>Wooding, S and H.R.B. Pelham, The dynamics of Golgi protein traffic visualized in living yeast cells. Molecular biology of the cell. 9: 2667-2680 1998</ref>

The [[Maturational model]] suggests that the new vesicles from the ER enter the cis Golgi network and retrograde vesicles (bearing COPI) coats move to merge with the cis region cisternae.  These carry Golgi complex processing enzymes and their targeting to this region may be dependent on the low concentration of these processing enzymes.  Then, as processing continues, the middle [[cisternae]] contain more mature product and lower amounts of the enzymes needed in the beginning.  Finally, the trans region is specialized for sorting, containing receptors to sort and isolate lysosomal enzymes, for example.<ref>Wooding, S and H.R.B. Pelham, The dynamics of Golgi protein traffic visualized in living yeast cells. Molecular biology of the cell. 9: 2667-2680 1998</ref>

===Protein transport to the rough endoplasmic reticulum===

===Protein transport to the rough endoplasmic reticulum===

[[Image:Gol2.jpg|Gol2.jpg]]

[[Image:Gol2.jpg|Gol2.jpg]]

This cartoon shows the process. The protein destined for secretion is red. The blue protein must remain in the rough endoplasmic reticulum. The rough endoplasmic reticulum has inserted a receptor protein on the membrane it sends to the Golgi complex in the transitional vesicles (shown in green).  These are retrograde vesicles and are therefore coated with "COPI" (coatamer).  The ER protein receptor captures all of the  protein that carries the ER residency signal. . Vesicles then bud from the Golgi complex and move back to the rough endoplasmic reticulum. The receptor can circulate and continue to return the proteins needed by the endoplasmic reticulum.

The diagram above shows the process. The protein destined for secretion is red. The blue protein must remain in the rough [[endoplasmic reticulum]]. The rough endoplasmic reticulum has inserted a receptor protein on the membrane it sends to the Golgi complex in the transitional vesicles (shown in green).  These are retrograde vesicles and are therefore coated with "COPI" (coatamer).  The ER protein receptor captures all of the  protein that carries the ER residency signal. . Vesicles then bud from the Golgi complex and move back to the rough endoplasmic reticulum. The receptor can circulate and continue to return the proteins needed by the endoplasmic reticulum.

==References==

==References==