The erythrocyte membrane maintains its biconcave disc shape through a spectrin–actin cytoskeletal network. Ankyrin links spectrin to which integral membrane protein, and how does this anchorage maintain cell deformability?

• A Glycophorin A; this linkage transmits shear forces directly to the actin core
• B Stomatin; ankyrin-stomatin interactions regulate Na⁺/K⁺-ATPase to maintain cell volume
• C CD47 (integrin-associated protein); ankyrin-CD47 linkage provides the 'don't eat me' signal
• D Band 3 protein (AE1); ankyrin-Band 3 linkage keeps the cytoskeleton tethered to the lipid bilayer, and the spectrin heterodimer meshwork's flexibility allows shape changes under shear stress without cell fragmentation ✓

Explanation

The primary cytoskeletal anchor is ankyrin (ankyrin R/ANK1) connecting spectrin tetramers to Band 3 (ankyrin-binding domain of AE1/SLC4A1). A second attachment point is protein 4.1R linking spectrin-actin to glycophorin C and CD44. The flexible hexagonal spectrin network distributes mechanical stress during passage through narrow capillaries, enabling reversible deformation. Mutations in spectrin (hereditary spherocytosis/elliptocytosis), ankyrin (most common cause of hereditary spherocytosis), or Band 3 weaken this network, causing membrane loss (micro-vesiculation) → spherocyte formation → reduced deformability → splenic hemolysis.

Reference: Guyton & Hall, Textbook of Medical Physiology, 14th ed.

High-yield for: NEET PGINI-CETNExTFMGEUSMLEPLABMRCP

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