Mild spherocytosis and altered red cell ion transport in protein 4. 2-null mice.
Protein 4.2 is a major component of the red blood cell (RBC) membrane skeleton. We used targeted mutagenesis in embryonic stem (ES) cells to elucidate protein 4.2 functions in vivo. Protein 4. 2-null (4.2(-/-)) mice have mild hereditary spherocytosis (HS). Scanning electron microscopy and ektacytometry confirm loss of membrane surface in 4.2(-/-) RBCs. The membrane skeleton architecture is intact, and the spectrin and ankyrin content of 4. 2(-/-) RBCs are normal. Band 3 and band 3-mediated anion transport are decreased. Protein 4.2(-/-) RBCs show altered cation content (increased K+/decreased Na+)resulting in dehydration. The passive Na+ permeability and the activities of the Na-K-2Cl and K-Cl cotransporters, the Na/H exchanger, and the Gardos channel in 4. 2(-/-) RBCs are significantly increased. Protein 4.2(-/-) RBCs demonstrate an abnormal regulation of cation transport by cell volume. Cell shrinkage induces a greater activation of Na/H exchange and Na-K-2Cl cotransport in 4.2(-/-) RBCs compared with controls. The increased passive Na+ permeability of 4.2(-/-) RBCs is also dependent on cell shrinkage. We conclude that protein 4.2 is important in the maintenance of normal surface area in RBCs and for normal RBC cation transport.
Peters
L L
LL
The Jackson Laboratory, Bar Harbor, Maine 04609, USA Department of Biomedical Research, St. Elizabeth's Medical Center, Boston, Massachusetts 02135, USA. luanne@aeetha.jax.org
Jindel
H K
HK
Gwynn
B
B
Korsgren
C
C
John
K M
KM
Lux
S E
SE
Mohandas
N
N
Cohen
C M
CM
Cho
M R
MR
Golan
D E
DE
Brugnara
C
C
D000818:Animals; D001457:Anion Exchange Protein 1, Erythrocyte / Q000378:metabolism; D001798:Blood Proteins / Q000235:genetics / Q000502:physiology*; D002412:Cations; D002463:Cell Membrane Permeability; D003598:Cytoskeletal Proteins; D004910:Erythrocyte Membrane / Q000378:metabolism / Q000648:ultrastructure; D004912:Erythrocytes / Q000378:metabolism* / Q000648:ultrastructure; D018390:Gene Targeting; D017136:Ion Transport; D008297:Male; D008565:Membrane Proteins; D051379:Mice; D008810:Mice, Inbred C57BL; D018345:Mice, Knockout; D010766:Phosphorylation; D011188:Potassium / Q000378:metabolism; D012964:Sodium / Q000378:metabolism; D013049:Spectrin / Q000378:metabolism; D013103:Spherocytosis, Hereditary / Q000097:blood / Q000209:etiology / Q000235:genetics / Q000378:metabolism*
D001457:Anion Exchange Protein 1, Erythrocyte; D001798:Blood Proteins; D002412:Cations; D003598:Cytoskeletal Proteins; D008565:Membrane Proteins; C044791:erythrocyte membrane band 4.2 protein; D013049:Spectrin; D012964:Sodium; D011188:Potassium