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Apical entry channels in calcium-transporting epithelia
Ji-Bin Peng1, Edward M Brown, Matthias A Hediger
1Membrane Biology Program and Renal Division, Department of Medicine, Brigham and Women's Hospital and Harvard Medical School, Boston, Massachusetts 02115, USA.
Summary
The study identified apical calcium channels CaT1 and ECaC, crucial for calcium absorption in epithelia. These channels are regulated by vitamin D, dietary calcium, and intracellular calcium levels, indicating their key role in transcellular calcium transport.
Area of Science:
- Physiology
- Molecular Biology
- Renal Physiology
Background:
- Transcellular calcium transport is vital for maintaining calcium homeostasis.
- Apical calcium entry is a critical and regulated step in this process.
- The molecular identity of apical calcium channels remained elusive until recent discoveries.
Purpose of the Study:
- To identify and characterize the molecular players responsible for apical calcium entry in calcium-transporting epithelia.
- To elucidate the regulatory mechanisms governing these apical calcium channels.
- To understand the role of these channels in the overall process of transcellular calcium transport.
Main Methods:
- Molecular cloning and expression of candidate calcium channels.
- Electrophysiological studies (e.g., patch-clamp) to assess channel function.
- In vivo and in vitro studies to investigate channel regulation by vitamin D, dietary calcium, and intracellular calcium.
Main Results:
- The apical calcium channels CaT1 (also known as TRPV6) and ECaC (also known as TRPV5) were identified as key mediators of apical calcium entry.
- Expression and activity of CaT1 and ECaC are regulated by vitamin D and dietary calcium levels.
- Intracellular calcium exerts feedback control on CaT1 and ECaC activity, suggesting a rate-limiting role.
Conclusions:
- CaT1 and ECaC are the primary molecular determinants of apical calcium entry in calcium-transporting epithelia.
- These channels are subject to complex regulation by hormonal (vitamin D) and nutritional (dietary calcium) factors, as well as intracellular calcium.
- The findings highlight the critical role of CaT1 and ECaC in regulating the rate of transcellular calcium transport and maintaining calcium balance.