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Albumin binding proteins are highly expressed in actively proliferating fetal and adult tissues
J Moroianu1, A Hillebrand, M Simionescu
1Institute of Cellular Biology and Pathology, Bucharest/Romania.
Insights
Albumin binding proteins (ABP) are present early in rabbit development and highly expressed in proliferating tissues like fetal organs and bone marrow, but not specific to any single tissue type.
Area of Science:
- Developmental Biology
- Biochemistry
- Immunology
Background:
- Albumin binding proteins (ABP) are peptides of 31 and 18 kDa.
- Their expression patterns during ontogenic development are not fully understood.
Purpose of the Study:
- To investigate the expression of ABP in various organs during different developmental stages in rabbits.
- To determine if ABP expression correlates with tissue proliferation and differentiation.
Main Methods:
- Ligand blotting and quantitative immunoblot assays were used on tissue extracts from rabbit embryos, fetuses, neonates, and adults.
- Proteins were detected using [125I]albumin and radioiodinated antibodies against the 31 kDa ABP.
Main Results:
- ABP were highly expressed in embryos and fetal organs.
- ABP expression decreased in neonatal and adult brain, heart, and skeletal muscle but remained stable in the lung.
- ABP were major proteins in adult bone marrow cells, thymocytes, and splenocytes, indicating high expression in proliferating cells.
Conclusions:
- ABP are present early in embryogenesis and are not tissue-specific.
- ABP expression is particularly high in organs and cells characterized by active proliferation and differentiation, suggesting a role in these processes.
Abstract:
The expression of albumin binding proteins (ABP, 31 and 18 kDa peptides) in various organs as a function of their ontogenic development was investigated in fetuses (20 days old), neonates (1 day old) and adult rabbits. At each of these stages, tissue extracts of brain, lung, thymus, heart, skeletal muscle and liver as well as whole embryos (11 days old) were examined by ligand blotting and quantitative immunoblot assays. Blots were either incubated with [125I]albumin followed by autoradiography and radioassay or exposed to a radioiodinated antibody raised against affinity-isolated 31 kDa peptide. Anti-31 kDa IgG cross-reacted with both 31 and 18 kDa peptides. Both methods used revealed that ABP are well expressed in embryos and in all fetal organs investigated. By comparison, in neonates, the ABP expression was diminished (by approximately 2-fold) in brain, heart and skeletal muscle. These changes were even more pronounced in the adult rabbit brain, heart, skeletal muscle and liver; no significant modification was detected in the lung. Prompted by these results, which inferred a high level of ABP in actively proliferating/differentiating tissues, we checked for the presence of ABP in other adult cells and tissues. In bone marrow cells, thymocytes and splenocytes, the 31 and 18 kDa peptides represented the major sodium dodecyl sulfate-urea extracted proteins, whereas in mature circulating white blood cells they were moderately expressed. The results indicate that ABP 1) are present early in embryogenesis, 2) are particularly well expressed in organs (fetal or adult) and cells characterized by active proliferation and differentiation, and 3) are not tissue specific.(ABSTRACT TRUNCATED AT 250 WORDS)