Human vitamin C (L-ascorbic acid) transporter SVCT1.

Area of Science:

• Molecular Biology
• Human Physiology
• Nutritional Science

Background:

• Vitamin C (l-ascorbic acid) is an essential micronutrient vital for numerous biological functions in humans, including enzymatic reactions and antioxidant defense.
• Understanding the molecular mechanisms of vitamin C transport is crucial for comprehending its metabolism and role in health and disease.

Purpose of the Study:

• To identify and characterize novel human cDNA encoding vitamin C transporters.
• To investigate the function, substrate specificity, and localization of these transporters.
• To map the genes responsible for these transporters and explore their potential association with diseases.

Main Methods:

• Molecular cloning of human cDNA.
• Expression of transporters in Xenopus oocytes.
• Radiotracer uptake assays and voltage-clamp electrophysiology.
• Gene mapping using human chromosome analysis.

Main Results:

• Molecular cloning of SVCT1, a novel human vitamin C transporter, primarily found in kidney and small intestine epithelia.
• SVCT1 mediates saturable, high-affinity, electrogenic l-ascorbic acid transport, inhibited by phloretin, with high substrate selectivity.
• The SLC23A2 gene (coding SVCT1) mapped to chromosome 5q31.2-31.3; SLC23A1 encodes SVCT2, a related transporter found in brain, retina, and endocrine tissues.

Conclusions:

• The molecular identification of human l-ascorbic acid transporters SVCT1 and SVCT2 provides essential tools for studying vitamin C metabolism.
• These transporters play critical roles in maintaining vitamin C homeostasis in various tissues.
• Further research can now focus on the implications of these transporters in human health and disease, including their potential link to leukemia.