L-aspartate import across plasma membrane

Definition

Target type: biologicalprocess

The directed movement of L-aspartate from outside of a cell, across the plasma membrane and into the cytosol. [GO_REF:0000069, PMID:7914198]

L-aspartate import across the plasma membrane is a crucial process for cellular metabolism and function. Aspartate, an amino acid, is an important precursor for various metabolic pathways, including the urea cycle, gluconeogenesis, and biosynthesis of purines and pyrimidines. Its transport across the plasma membrane is primarily mediated by specific transporter proteins.

The most well-characterized transporter for L-aspartate is the sodium-coupled aspartate transporter (ASCT2). ASCT2 is a member of the solute carrier family 1, which encompasses a broad range of membrane transporters with diverse substrate specificities. ASCT2 is a symporter, meaning it co-transports L-aspartate along with sodium ions across the plasma membrane. This process is driven by the electrochemical gradient of sodium ions, which are typically higher outside the cell.

The transport cycle of ASCT2 can be summarized as follows:

1. **Binding of sodium and aspartate:** ASCT2 has binding sites for both sodium ions and L-aspartate. The binding of sodium ions to the transporter is essential for its conformational changes and subsequent aspartate uptake.
2. **Conformational change:** Upon sodium binding, ASCT2 undergoes a conformational shift, exposing the aspartate binding site to the extracellular space.
3. **Aspartate uptake:** The conformational change allows L-aspartate to bind to the transporter.
4. **Translocation:** The transporter, with both sodium and aspartate bound, undergoes another conformational change, translocating the substrates to the intracellular side of the membrane.
5. **Release and recycling:** Once inside the cell, sodium and aspartate dissociate from the transporter. The transporter returns to its original conformation, ready to initiate another transport cycle.

The activity of ASCT2 is regulated by various factors, including:

- **Sodium concentration:** The influx of sodium ions is critical for ASCT2 function.
- **Membrane potential:** The electrical potential across the plasma membrane can influence the transport rate.
- **pH:** ASCT2 activity is sensitive to pH changes.
- **Hormones and signaling pathways:** Various hormones and signaling pathways can modulate ASCT2 expression and activity.

In addition to ASCT2, other transporters may also contribute to L-aspartate import, including:

- **System L:** A sodium-independent transporter with broad substrate specificity, including aspartate.
- **Glutamate transporters:** Certain glutamate transporters can transport aspartate as a secondary substrate.

The precise role of each transporter in aspartate import can vary depending on cell type and physiological conditions. However, the overall process of L-aspartate uptake across the plasma membrane is essential for maintaining cellular homeostasis and supporting diverse metabolic processes.'
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Proteins (5)

Compounds (25)