Red blood cell Na pump: Insights from species differences

Area of Science:

• Cellular biology
• Membrane transport
• Biochemistry

Background:

• Red blood cell membranes facilitate chloride-bicarbonate exchange, typically coupling pH gradients, chloride ratios, and membrane potential.
• Understanding how to independently alter intracellular and extracellular pH in red cells is crucial for studying membrane transport dynamics.

Purpose of the Study:

• To review evidence enabling separate manipulation of intracellular and extracellular pH in red blood cells.
• To examine the impact of pH on sodium (Na(+)) pump activity and transporter selectivity.
• To explore species-specific differences in red blood cell maturation and membrane protein loss.

Main Methods:

• Literature review of studies on red blood cell pH regulation and ion transport.
• Analysis of data concerning the effect of pH on Na(+) pump activity and transporter selectivity.
• Examination of research on reticulocyte maturation and membrane protein expression.

Main Results:

• Extracellular transport sites show decreased selectivity at high pH, becoming more selective with increased protons, with species-specific pK values.
• Intracellular transport sites are highly selective for Na(+) at high pH, becoming less selective with increased protons.
• Reticulocyte maturation involves species-dependent loss of membrane proteins, including Na(+) pumps, with Carnivora losing all pumps.

Conclusions:

• pH significantly influences the selectivity and activity of red blood cell membrane transporters.
• Species-specific variations in red blood cell maturation, particularly Na(+) pump loss, are notable.
• Protein kinase C (PKC) phosphorylation may play a role in endocytosis and species variation in membrane protein regulation.