mitochondria-associated endoplasmic reticulum membrane contact site

Definition

Target type: cellularcomponent

A zone of apposition between endoplasmic-reticulum and mitochondrial membranes, structured by bridging complexes. These contact sites are thought to facilitate inter-organelle calcium and phospholipid exchange. [GOC:jl, PMID:19556461, PMID:22078959, PMID:29626751, PMID:29684109]

Mitochondria-associated endoplasmic reticulum membrane contact sites (MAMs) are specialized regions where the endoplasmic reticulum (ER) and mitochondria come into close proximity. These sites are crucial for a variety of cellular processes, including lipid metabolism, calcium signaling, and apoptosis.

MAMs are characterized by the presence of specific proteins that mediate the interaction between the ER and mitochondrial membranes. These proteins include:

* **Mitofusin 2 (Mfn2):** A transmembrane protein that facilitates the tethering of the ER and mitochondrial membranes.
* **Voltage-dependent anion channel (VDAC):** A mitochondrial outer membrane channel that allows for the exchange of molecules between the mitochondria and the cytosol.
* **Phosphatidylinositol 4-kinase IIIβ (PI4KB):** An enzyme that produces phosphatidylinositol 4-phosphate (PI4P), a lipid involved in the formation of MAMs.

MAMs play a critical role in lipid metabolism by facilitating the transfer of lipids, such as phosphatidylcholine and cholesterol, between the ER and mitochondria. This exchange is essential for mitochondrial membrane biogenesis and for the production of steroid hormones.

MAMs also play a key role in calcium signaling. Calcium ions released from the ER can travel to the mitochondria through MAMs, where they trigger a variety of cellular responses, including the activation of mitochondrial enzymes and the induction of apoptosis.

Finally, MAMs are involved in apoptosis, the process of programmed cell death. When cells are exposed to stress, MAMs can release pro-apoptotic factors, such as cytochrome c, from the mitochondria into the cytosol, triggering the apoptotic cascade.

In summary, MAMs are highly dynamic and essential cellular compartments that mediate communication and exchange between the ER and mitochondria. These sites are crucial for a variety of cellular processes, including lipid metabolism, calcium signaling, and apoptosis.'
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Proteins (1)

Compounds (8)