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Immunoperoxidase localization of apolipoprotein D in human enterocytes and hepatocytes
M E Bouma1, J P de Bandt, M Ayrault-Jarrier
1INSERM Unité 9, Hôpital Saint-Antoine, Paris, France.
Abstract:
In this study we prepared a pure apolipoprotein D and obtained a specific antiserum to it. The purified apolipoprotein D migrated as a single band of Mr = 29,000 but appeared as five isoforms on isoelectrofocusing. The antiserum did not cross-react with other apolipoproteins. Immunoenzymatic staining revealed the presence of apolipoprotein D in the perinuclear area of the cytoplasm of isolated normal hepatocytes and HepG2 cells. Apolipoprotein D was also localized in intestinal epithelium and in liver cells. The intracellular distribution of apolipoprotein D was similar to that of apolipoprotein B. Our results indicated that apolipoprotein D, like many other circulating apolipoproteins, is synthesized in enterocytes and hepatocytes.
Insights
Researchers purified apolipoprotein D and developed a specific antibody. This study found apolipoprotein D is synthesized in liver cells (hepatocytes) and intestinal cells (enterocytes).
Area of Science:
- Biochemistry
- Cell Biology
- Molecular Biology
Background:
- Apolipoprotein D (ApoD) is a lipid-binding protein found in plasma.
- Its precise cellular origin and synthesis sites have not been fully elucidated.
Purpose of the Study:
- To purify apolipoprotein D and generate a specific antiserum.
- To determine the cellular localization and synthesis sites of apolipoprotein D.
Main Methods:
- Purification of apolipoprotein D.
- Generation of a specific antiserum against apolipoprotein D.
- Isoelectrofocusing and SDS-PAGE for protein characterization.
- Immunoenzymatic staining for cellular localization.
Main Results:
- Purified apolipoprotein D showed a single band (Mr = 29,000) on SDS-PAGE but existed as five isoforms on isoelectrofocusing.
- The generated antiserum was specific for apolipoprotein D, showing no cross-reactivity with other apolipoproteins.
- Apolipoprotein D was detected in the perinuclear cytoplasm of hepatocytes and HepG2 cells, as well as in intestinal epithelium.
- Intracellular distribution of apolipoprotein D resembled that of apolipoprotein B.
Conclusions:
- Apolipoprotein D is synthesized in both hepatocytes and enterocytes.
- These findings suggest apolipoprotein D, similar to other circulating apolipoproteins, originates from these key synthetic sites.