VI. Clinical Correlations of Plasma Membrane Dysfunction
Defects or dysregulation of plasma membrane components are central to the pathology of numerous diseases.
| Condition | Associated Membrane Component | Pathophysiology / Result |
| Hereditary Spherocytosis | Spectrin, Band 4.1 protein | Defective spectrin has a decreased ability to bind to band 4.1 protein, resulting in fragile, misshapen red blood cells (spherocytes) and anemia. |
| Diffuse Axonal Injury | Spectrin | Shearing forces (e.g., in car accidents, shaken baby syndrome) cause irreparable cleavage of spectrin, destroying the neuronal cytoskeleton and leading to cell death. |
| Cystinuria | Carrier Proteins | Abnormal carrier proteins fail to remove cystine from urine, leading to the formation of kidney stones. |
| Multidrug Resistance in Cancer | ABC-Transporters (MDR proteins) | Cancer cells express transporters that actively pump cytotoxic drugs out of the cell, rendering chemotherapy ineffective. |
| Snake Venom Poisoning | Acetylcholine Receptors | Venom inactivates acetylcholine receptors at neuromuscular junctions, leading to progressive muscle paralysis. |
| Graves’ Disease | Plasma Membrane Receptors | An autoimmune disease where antibodies bind to and activate thyroid-stimulating hormone receptors, causing hyperthyroidism. |
| Cholera | Gs (stimulatory G protein) | Cholera toxin modifies Gs protein, causing it to remain active. This leads to excessive cAMP levels in intestinal cells, causing severe diarrhea. |
| Whooping Cough (Pertussis) | Gi (inhibitory G protein) | Pertussis toxin modifies Gi proteins, causing an accumulation of the inactive form and leading to irritation of bronchial passages. |
| Genetic Gs Protein Defects | Gs (stimulatory G protein) | Defective Gs proteins can lead to mental retardation, diminished growth and sexual development, and decreased responses to certain hormones. |
| Anesthetic Action (Probable) | Ligand-gated Ion Channels | Anesthetic agents are thought to act on these channels to block the spread of action potentials. |