An exocyst is an octameric protein complex involved in the transport of vesicles that binds and addresses the delivery of vesicles that leave the Golgi apparatus to the plasma membrane immediately before their fusion. The complex is involved in a number of intracellular processes, including exocytosis , cell movement and growth [1] . The components of this complex are often located in the shape of a crescent at the tip of the growing hyphae, in the immediate vicinity of Spitzenkörper , and can even bind to its vesicles [2] .
Content
Subunits
In mammalian and human cells, this complex is represented by the following eight proteins: EXOC1 , EXOC2 , EXOC3 , EXOC4 , EXOC5 , EXOC6 , EXOC7 , and EXOC8 . In invertebrates such as Drosophila melanogaster , as well as fungi, these subunits are known as Sec3, Sec5, Sec6, Sec8, Sec10, Sec15, Exo70, and Exo84. All these proteins interact, including with factors that control polar growth: Rho GTPase Cdc42 , Rho I , Rho3 , Sec4 and Rab , located on the surface of the vesicle membrane, and with secretion proteins. Exocyst proteins occupy a boundary position between the processes of polar growth and secretion [1] .
Functions
The exocyst complex serves to direct the vesicles that leave the Golgi apparatus to certain places in the cell membrane, for their docking and subsequent fusion with it. For this reason, the complex is actively involved in exocytosis . Sec3 (EXOC1) and Exo70 (EXOC7) are located on the plasma membrane and are physically associated with Rho GTPases , for example, CDC42 . Other exocyst components — Sec15 (EXOC6) and Sec4 — are located on the vesicle membrane. Exocyst proteins located on the plasma membrane bind exocyst proteins on the vesicle membrane, as a result of which the vesicle is attached to the membrane and merges quite easily with it. Similarly, SNARE proteins act by fusing intracellular transport vesicles to the cell membrane [3] .
The exocyst also interacts with Rho GTPases responsible for controlling cell polarity and cytoskeletal activity.
See also
- Exocytosis
Links
Notes
- ↑ 1 2 Kamzolkina, 2015 , p. 66.
- ↑ Kamzolkina, 2015 , p. 70.
- ↑ Kamzolkina, 2015 , p. 68.
Literature
- Kamzolkina O. V., Dunaevsky Y. E. Biology of the mushroom cell. - M .: Partnership of scientific publications of KMK, 2015. - 239 p. - ISBN 978-5-9906564-1-3 .