TRPC4 forms store-operated Ca2+ channels in mouse mesangial cells.

Area of Science:

• Nephrology
• Molecular Biology
• Cell Physiology

Background:

• Store-operated calcium (SOC) channels are critical for regulating intracellular calcium levels in various cell types.
• The canonical transient receptor potential (TRPC) protein family is known to form cation channels, but their specific role in mesangial cells (MMC) was unclear.

Purpose of the Study:

• To identify the specific TRPC protein(s) responsible for SOC activity in murine mesangial cells (MMC).
• To elucidate the role of identified TRPC proteins in mediating calcium influx in MMC.

Main Methods:

• Reverse transcription polymerase chain reaction (RT-PCR) was used to screen for TRPC mRNA expression in MMC.
• Immunocytochemistry was employed to determine the cellular localization of TRPC proteins.
• Fura 2 ratiometric measurements assessed intracellular calcium concentration ([Ca(2+)](i)) changes.
• TRPC4 antisense oligonucleotides were used to inhibit TRPC4 expression and evaluate its effect on SOC.

Main Results:

• MMC expressed mRNA for TRPC1 and TRPC4, but not other TRPC subtypes.
• TRPC1 showed predominantly cytoplasmic expression, while TRPC4 was localized to the plasma membrane.
• TRPC4 antisense significantly inhibited SOC by 83%, while scrambled oligonucleotides had no effect.
• TRPC4 expression was confirmed in mouse renal glomeruli, with TRPC4-alpha isoform identified in MMC.

Conclusions:

• TRPC4, specifically the TRPC4-alpha isoform, is a major component of the store-operated calcium channel in mouse mesangial cells.
• TRPC4-alpha likely forms the homotetrameric channel responsible for SOC in MMC.
• These findings contribute to understanding calcium signaling in kidney cells and potential therapeutic targets.