Hypertonic induction of the cell adhesion molecule beta 1-integrin in MDCK cells.
Cells of many organisms adapt to osmotic stress by accumulating compatible organic osmolytes. In Madin-Darby canine kidney (MDCK) cells, a renal epithelial cell line widely used as a culture model for the study of osmotic regulation in mammals, extracellular hypertonicity induces genes responsible for the accumulation of organic osmolytes. We have recently cloned from these cells a partial cDNA corresponding to a member of the transmembrane 4 superfamily (tetraspan) family, CD9 antigen, and demonstrated its induction by hypertonicity [D. Sheikh-Hamad, J. D. Ferraris, J. Dragolovich, H. G. Preuss, M. B. Burg, and A. García-Pérez. Am. J. Physiol. 270 (Cell Physiol. 39): C253-C258, 1996]. An association between CD9 and potential regulatory proteins, such as the heparin-binding epidermal growth factor-like protein and the cell adhesion molecule beta 1-integrin, has been reported. Here, using beta 1-integrin-specific monoclonal antibodies and an antisense oligonucleotide probe, we demonstrate expression and hypertonic induction of beta 1-integrin in MDCK cells. Induction of the mRNA and protein occurs in 2 h and is maximal at 6 h, consistent with a regulatory role in the adaptation to osmotic stress. In addition, we show that accumulation of organic osmolytes markedly attenuates the hypertonic induction of the mRNA, a feature shared with genes involved in hyperosmotic stress response. Finally, we demonstrate that CD9 and beta 1-integrin are expressed in association at the cell membrane. Our findings suggest the existence of a cluster of integral membrane proteins that includes but may not be limited to CD9 and the adhesion molecule beta 1-integrin, which may play a role in the adaptation of kidney cells to osmotic stress, possibly at the regulatory level.
Sheikh-Hamad
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Department of Medicine, Baylor College of Medicine, Houston, Texas 77030, USA.
Suki
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Zhao
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D000818:Animals; D001483:Base Sequence; D002460:Cell Line; D002462:Cell Membrane / Q000502:physiology; D002522:Chlorocebus aethiops; D004285:Dogs; D004848:Epithelium; D006982:Hypertonic Solutions; D019012:Integrin beta1 / Q000096:biosynthesis*; D007668:Kidney; D008969:Molecular Sequence Data; D016376:Oligonucleotides, Antisense; D012333:RNA, Messenger / Q000096:biosynthesis; D014158:Transcription, Genetic; D014709:Vero Cells; D014882:Water-Electrolyte Balance
D006982:Hypertonic Solutions; D019012:Integrin beta1; D016376:Oligonucleotides, Antisense; D012333:RNA, Messenger