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Heat- and PIP2-dependent TRPM4 activity underlies mutually exclusive human diseases
Yuhua Tian1,2, Soohyeon Bae3, Xuesong Wu4
1Department of Pharmacology, School of Pharmacy, Qingdao University, Qingdao 266071, China.
Abstract:
Temperature-sensitive transient receptor potential melastatin subfamily 4 (TRPM4) ion channels convert intracellular calcium increases into membrane depolarization, thereby linking these two powerful cellular signaling pathways in diverse physiological processes. TRPM4 mutations cause severe human hereditary cardiovascular and skin diseases; mysteriously, while these mutations are gain-of-function in nature, they affect the heart and the skin in a mutually exclusive manner. Here, we show that phosphatidylinositol 4,5-bisphosphate (PIP2) lipid is a required cofactor for TRPM4 activity by tightly regulating its calcium sensitivity. We detected two PIP2 binding sites and located the high-affinity site adjacent to the S4-S5 linker. We demonstrated that skin disease-associated TRPM4 mutations relieve the tight control of PIP2, resulting in elevated channel activity but only at the body surface temperature. In contrast, heart diseases are associated with mutations known to boost the number of channels, an effect we found to be annihilated by channel desensitization outside the body core. Indeed, dendritic cells from transgenic mice carrying a skin disease mutant exhibited elevated migration at 25-to-30°C range compared to those from normal mice, but no difference was observed at 37°C. These findings shed light on a molecular mechanism for dynamic regulation of cellular signaling in physiology and diseases.
Insights
Phosphatidylinositol 4,5-bisphosphate (PIP2) regulates temperature-sensitive TRPM4 channels. Mutations causing skin disease enhance TRPM4 activity at body surface temperatures, while heart disease mutations are counteracted by cooler temperatures.
Area of Science:
- Molecular Biology
- Cellular Signaling
- Ion Channel Physiology
Background:
- Transient Receptor Potential Melastatin 4 (TRPM4) channels link calcium signaling and membrane depolarization.
- TRPM4 mutations cause hereditary cardiovascular and skin diseases, affecting tissues differently despite being gain-of-function.
- The precise molecular mechanisms underlying tissue-specific disease manifestation remain unclear.
Purpose of the Study:
- To investigate the role of phosphatidylinositol 4,5-bisphosphate (PIP2) in TRPM4 channel regulation.
- To elucidate the molecular basis for the tissue-specific effects of TRPM4 mutations in cardiovascular and skin diseases.
Main Methods:
- Identification and characterization of PIP2 binding sites on TRPM4.
- Analysis of TRPM4 channel activity in response to temperature and PIP2 levels.
- Assessment of cellular migration in transgenic mouse models with skin disease-associated TRPM4 mutations.
Main Results:
- PIP2 acts as a critical cofactor for TRPM4 activity, modulating its calcium sensitivity.
- Two PIP2 binding sites were identified, with one high-affinity site near the S4-S5 linker.
- Skin disease mutations disrupt PIP2 regulation, increasing TRPM4 activity at lower temperatures (25-30°C) but not core body temperature (37°C).
- Cardiovascular disease mutations leading to increased channel numbers are counteracted by desensitization at cooler temperatures.
Conclusions:
- PIP2 is essential for the proper temperature-dependent function of TRPM4 channels.
- Differential regulation of TRPM4 by PIP2 and temperature explains the tissue-specific pathologies observed in hereditary cardiovascular and skin diseases.
- These findings reveal a molecular mechanism for dynamic cellular signaling regulation in health and disease.
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