AJP - Cell Physiology, Vol 260, Issue 6 C1308-C1314, Copyright © 1991 by American Physiological Society
Toad urinary bladder epithelial cells contain an analogue of cytoskeletal protein 4.1
L. M. Guay-Woodford, O. Platt and H. W. Harris Jr
Division of Nephrology, Children's Hospital, Boston, Massachusetts.
Epithelial cell polarity and vectorial transport require cytoskeletal
proteins that maintain local cell membrane structure and mediate
cytoplasmic vesicle movement. The cytoskeleton of leaky epithelia, such as
the intestinal mucosa and renal proximal tubule cells, has been extensively
studied. However, cytoskeletal studies in tight epithelia such as the
mammalian collecting duct and toad urinary bladder generally have been
confined to ultrastructural investigation. Recent research in nonepithelial
cell types has identified an interesting family of cytoskeletal proteins.
Present in multiple cell types, these protein 4.1 analogues share a number
of similar functional characteristics, yet are structurally diverse. They
are multiply phosphorylated by several different kinases, and
phosphorylation regulates their associations with other cytoskeletal
constituents, integral membrane components, and cytoplasmic vesicles. Using
a combination of immunochemical and immunofluorescent techniques, we have
demonstrated that toad bladder epithelial cells contain a 65-kDa analogue
of human erythrocyte protein 4.1. Toad bladder epithelial cell protein 4.1
is structurally similar to its erythrocyte counterpart and is
phosphorylated. This protein 4.1 species is present throughout the toad
bladder granular cell cytoplasm, suggesting that it participates in
multiple granular cell functions.
