Glycoproteins and glycolipids of rat small intestinal microvillus and basolateral membranes
A Morita1, B Siddiqui, R H Erickson
1Gastrointestinal Research Laboratory, Veterans Administration Medical Center, San Francisco, California 94121.
Abstract:
Glycoprotein and glycolipid constituents were examined in purified microvillus and basolateral membranes isolated from rat small intestinal epithelial cells. SDS-polyacrylamide gel electrophoresis showed that the molecular weights of most of the major proteins from microvillus membranes were over 100 kD, whereas the majority of those from basolateral membranes tended to have lower molecular weights. Glycoprotein profiles were also examined using three labeling methods, and in each case marked differences were observed between microvillus and basolateral membranes. In both membranes, lectins with a specificity toward N-linked sugar chains bound to the majority of the glycoproteins, in contrast to those lectins which preferentially bind to O-linked sugar chains. Glycolipids were labeled in vivo and isolated from both membrane fractions. Some differences were observed in the fucolipids and neutral glycolipids suggesting a more complex pattern in microvillus membranes. These results indicate that there are differences in the glycoprotein and glycolipid compositions of microvillus and basolateral membranes that may reflect the functional polarity of intestinal epithelial cells.
Insights
This study reveals distinct glycoprotein and glycolipid profiles in rat intestinal epithelial cell membranes. These differences in microvillus and basolateral membranes suggest specialized functions for these cell compartments.
Area of Science:
- Cell Biology
- Biochemistry
- Gastroenterology
Background:
- Intestinal epithelial cells possess distinct apical (microvillus) and basolateral membrane domains.
- These domains exhibit specialized protein and lipid compositions crucial for their functions.
Purpose of the Study:
- To investigate and compare the glycoprotein and glycolipid constituents of microvillus and basolateral membranes from rat small intestinal epithelial cells.
- To identify differences that may correlate with the functional polarity of these cells.
Main Methods:
- Isolation of purified microvillus and basolateral membrane fractions from rat small intestinal epithelial cells.
- Analysis of protein molecular weights using SDS-polyacrylamide gel electrophoresis.
- Examination of glycoprotein profiles using three distinct labeling methods and lectin binding.
- In vivo labeling and isolation of glycolipids from both membrane fractions.
Main Results:
- Microvillus membrane proteins predominantly exhibited higher molecular weights (>100 kD) compared to basolateral membrane proteins.
- Significant differences in glycoprotein profiles were observed between the two membrane types.
- Both membrane types showed a preference for N-linked sugar chains over O-linked sugar chains in their glycoproteins.
- Glycolipid analysis revealed more complex patterns in microvillus membranes, particularly concerning fucolipids and neutral glycolipids.
Conclusions:
- Microvillus and basolateral membranes of intestinal epithelial cells display unique glycoprotein and glycolipid compositions.
- These compositional differences likely underpin the specialized functions of each membrane domain.
- The findings support the concept of functional and molecular polarity within intestinal epithelial cells.
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