Mutations affecting G-protein subunit α11 in hypercalcemia and hypocalcemia

Area of Science:

• Endocrinology
• Genetics
• Molecular Biology

Background:

• Familial hypocalciuric hypercalcemia (FHH) is a genetic disorder with three types.
• Type 1 FHH involves calcium-sensing receptor (CASR) loss-of-function mutations.
• Type 3 FHH is linked to AP2S1 mutations affecting CASR endocytosis.

Purpose of the Study:

• To investigate the role of GNA11 mutations in FHH type 2.
• To determine if GNA11 gain-of-function mutations cause hypocalcemia.

Main Methods:

• GNA11 mutational analysis in FHH and hypocalcemia patients.
• In vitro expression studies of GNA11 mutations in HEK293 cells.
• Assessment of Gα11 protein structure and CASR signaling.

Main Results:

• Identified GNA11 loss-of-function mutations (Ile200del, Leu135Gln) in FHH type 2 patients.
• Detected GNA11 gain-of-function mutations (Arg181Gln, Phe341Leu) in autosomal dominant hypocalcemia type 2 patients.
• Demonstrated that FHH-associated mutations decrease cell sensitivity to calcium, while hypocalcemia-associated mutations increase it.

Conclusions:

• Gα11 loss-of-function mutations cause familial hypocalciuric hypercalcemia type 2.
• Gα11 gain-of-function mutations cause autosomal dominant hypocalcemia type 2.
• These findings elucidate the distinct roles of Gα11 in calcium homeostasis.