calcium ion export across plasma membrane

Definition

Target type: biologicalprocess

The directed movement of calcium ions from inside of a cell, across the plasma membrane and into the extracellular region. [GOC:mah, PMID:2145281]

Calcium ion export across the plasma membrane is a crucial cellular process that regulates intracellular calcium levels and plays vital roles in various physiological functions. This process involves the movement of calcium ions from the cytoplasm, the fluid inside cells, to the extracellular space, the environment surrounding cells.

Calcium export across the plasma membrane is primarily mediated by specialized transmembrane proteins known as calcium pumps, specifically plasma membrane calcium ATPases (PMCAs). These pumps utilize the energy from ATP hydrolysis to actively transport calcium ions against their concentration gradient, moving them from the low-calcium environment of the cytoplasm to the high-calcium environment outside the cell.

There are three major mechanisms involved in calcium export:

**1. Plasma Membrane Calcium ATPases (PMCAs):** PMCAs are the primary calcium pumps responsible for maintaining low intracellular calcium levels. They actively transport calcium ions out of the cell using the energy derived from ATP hydrolysis.

**2. Sodium-Calcium Exchanger (NCX):** The NCX is a secondary active transporter that utilizes the electrochemical gradient of sodium ions to drive calcium ion export. It exchanges three sodium ions entering the cell for one calcium ion leaving the cell.

**3. Calcium-activated Chloride Channels (CaCCs):** CaCCs contribute to calcium export by indirectly facilitating calcium efflux. They allow chloride ions to move across the membrane, which can create a negative membrane potential that promotes calcium ion export through other channels.

The efficiency and regulation of calcium export across the plasma membrane are crucial for maintaining cellular homeostasis. Disruptions in this process can lead to various cellular malfunctions and diseases.

Regulation of calcium export is achieved through several mechanisms, including:

**1. Phosphorylation:** The activity of PMCAs can be modulated by phosphorylation, which can either activate or inhibit their activity.

**2. Calcium Binding:** Calcium itself can regulate the activity of some calcium pumps and exchangers, leading to feedback mechanisms.

**3. Interactions with other proteins:** PMCAs and NCXs can interact with other proteins, which can influence their activity and localization within the membrane.

Overall, calcium ion export across the plasma membrane is a complex process involving specialized proteins and intricate regulatory mechanisms. This process is essential for maintaining cellular calcium homeostasis, ensuring normal cell function, and preventing cellular dysfunction.'
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