ABCC8 and ABCC9: ABC transporters that regulate K+ channels

Area of Science:

• Molecular Biology
• Cell Physiology
• Biochemistry

Background:

• Sulfonylurea receptors (SURs) ABCC8/SUR1 and ABCC9/SUR2 are part of the ATPase superfamily, uniquely partnered with K+ pores (KIR6.1/KCNJ8 or KIR6.2/KCNJ11) to form ATP-sensitive potassium (KATP) channels.
• These KATP channels are vital in endocrine cells, neurons, and muscle tissues, playing a key role in cellular energy sensing and function.

Purpose of the Study:

• To elucidate the regulatory mechanisms of KATP channel activity by adenine nucleotides and the role of SUR subunits.
• To investigate the impact of mutations in SUR and K+ pore subunits on channel function and associated human diseases.
• To explore the physiological roles of KATP channels in various tissues using genetic models.

Main Methods:

• Biochemical assays to study nucleotide binding and hydrolysis on SUR subunits.
• Electrophysiological recordings to assess KATP channel activity.
• Genetic studies, including analysis of mutations and KATP channel null mice models.

Main Results:

• Adenine nucleotides exhibit dual regulation: inhibition via pore binding and stimulation via SUR nucleotide-binding domains.
• Mutations in SUR1/KIR6.2 channels are linked to monogenic disorders such as hyperinsulinemic hypoglycemia and neonatal diabetes.
• KIR6.2 polymorphism is implicated as a risk factor for type 2 diabetes mellitus, highlighting KATP channel dysregulation in metabolic disease.

Conclusions:

• KATP channels are critical regulators of cellular function, with SUR subunits playing a central role in their modulation.
• Dysregulation of KATP channels due to mutations or polymorphisms has significant implications for human health, contributing to endocrine and metabolic disorders.
• Ongoing research, particularly using KATP channel null mice, continues to reveal the diverse physiological functions of these metabolically sensitive channels.