TY - JOUR
T1 - Intracellular transport and processing of secretory component in cultured rat hepatocytes
AU - Musil, Linda S.
AU - Baenziger, Jacques U.
N1 - Funding Information:
Received November 12, 1986. Accepted July 13, 1987. Address requests for reprints to: Jacques U. Baenziger, Department of Pathology, Box 8118, Washington University School of Medicine, 660 South Euclid Avenue, St. Louis, Missouri 63110. This work was supported by grant R37-CA21923 from the U.S. Public Health Service and in part by the Monsanto/Washington University Biomedical Research Grant. L. S. Musil was supported by the Training Program in Cellular and Molecular Biology, U.S. Public Health Service grant 5 T32 GM07067 and National Institutes of Health Grant in Mechanisms of Disease in Environmental Pathology T32 ES07066-09. The authors thank Dr. B. Underdown (University of Toronto) for antiserum to native rat fSC and Dr. S. Cullen (Washington University) for S. aureus cells. 0 1987 by the American Gastroenterological 0016-5085/87/$3.50
PY - 1987/12
Y1 - 1987/12
N2 - Membrane secretory component (mSC) mediates the transcellular transport of polymeric immunoglobulin A from the sinusoidal surface of rat hepatocytes to the bile, where it is released as a proteolytic fragment, fSC. We have examined the biosynthesis, posttranslational processing, transport, and cleavage of secretory component in cultured rat hepatocytes. Membrane secretory component is detected at the cell surface beginning 1.0-1.5 h after synthesis, whereas fSC is not found in the medium until 2.5-3 h after synthesis. Approximately 16% of metabolically labeled mSC is accessible at the cell surface at 4 °C. Surface accessible mSC labeled with 125I at 4 °C is internalized with a half-time of <5 min after warming to 37 °C and begins to be released as fSC after 20 min at 37 °C. Posttranslational processing and cleavage of mSC by cultured hepatocytes yields products that appear to be identical to those produced in vivo. Although the kinetics of some of these events are significantly slower than those observed in vivo, the major fraction of mSC accessible at the surface of cultured hepatocytes is internalized before cleavage to fSC, as occurs with mSC present on the sinusoidal domain of hepatocytes in vivo. Cultured hepatocytes provide a suitable model system for the examination of mSC transport and cleavage to fSC.
AB - Membrane secretory component (mSC) mediates the transcellular transport of polymeric immunoglobulin A from the sinusoidal surface of rat hepatocytes to the bile, where it is released as a proteolytic fragment, fSC. We have examined the biosynthesis, posttranslational processing, transport, and cleavage of secretory component in cultured rat hepatocytes. Membrane secretory component is detected at the cell surface beginning 1.0-1.5 h after synthesis, whereas fSC is not found in the medium until 2.5-3 h after synthesis. Approximately 16% of metabolically labeled mSC is accessible at the cell surface at 4 °C. Surface accessible mSC labeled with 125I at 4 °C is internalized with a half-time of <5 min after warming to 37 °C and begins to be released as fSC after 20 min at 37 °C. Posttranslational processing and cleavage of mSC by cultured hepatocytes yields products that appear to be identical to those produced in vivo. Although the kinetics of some of these events are significantly slower than those observed in vivo, the major fraction of mSC accessible at the surface of cultured hepatocytes is internalized before cleavage to fSC, as occurs with mSC present on the sinusoidal domain of hepatocytes in vivo. Cultured hepatocytes provide a suitable model system for the examination of mSC transport and cleavage to fSC.
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U2 - 10.1016/0016-5085(87)90244-7
DO - 10.1016/0016-5085(87)90244-7
M3 - Article
C2 - 3678737
AN - SCOPUS:0023618286
SN - 0016-5085
VL - 93
SP - 1194
EP - 1204
JO - Gastroenterology
JF - Gastroenterology
IS - 6
ER -