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Calcium‐dependent peripheral localization of 4.1‐like proteins and fodrin in cultured human keratinocytes
Author(s) -
Shimizu Tadamichi,
Takakuwa Yuichi,
Koizumi Hiroko,
Ishibashi Teruo,
Ohkawara Akira
Publication year - 1996
Publication title -
biology of the cell
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 1.543
H-Index - 85
eISSN - 1768-322X
pISSN - 0248-4900
DOI - 10.1111/j.1768-322x.1996.tb00951.x
Subject(s) - cytoplasm , biology , spectrin , microbiology and biotechnology , cytosol , actin , membrane protein , cytoskeleton , cell membrane , cell , peripheral membrane protein , skeletal muscle , integral membrane protein , biochemistry , membrane , anatomy , enzyme
Summary— Recently, several proteins immunologically related to erythrocyte membrane skeletal proteins, such as protein 4.1 and fodrin (non‐erythroid spectrin), have been found in keratinocytes. In the present study, in order to investigate the roles of these proteins in cell‐cell contact, we analyzed the distribution of non‐erythroid protein 4.1, β‐fodrin and actin in cultured human keratinocytes at low (0.15 mM) and standard (1.85 mM) Ca 2+ concentrations. Immunofluorescence microscopy revealed that immunoreactive forms of protein 4.1, β‐fodrin and actin filaments were present in the cytoplasm of cells cultured in low Ca 2+ medium, while in cells in the standard Ca 2+ medium, these proteins were localized at the cell boundary and partially in the cytoplasm. When cells in the low‐Ca 2+ medium were treated with 100 nM 12‐O‐tetradecanoylphorbol‐13‐acetate (TPA) for 1 h, these proteins were also present at the cell boundary. Increasing extracellular Ca 2+ concentration from low to standard in the medium induces cell‐cell contact among the cultured human keratinocytes, accompanied by the translocation of protein 4.1 and β‐fodrin from the cytoplasm to the membrane. On the basis of the present study, movement of membrane skeletal proteins from the cytosol to the membrane suggests that either these proteins or the membrane skeletal lattice plays an important role in the regulation of cell‐cell intergigitations in response to changes in the Ca 2+ concentrations in culture medium, and that phosphorylation of these skeletal proteins might be involved in the regulation of the membrane skeletal proteins of keratinocytes in response to Ca 2+ .