Preparation of NSC Project Reports
Date Issued
2004-07-31
Date
2004-07-31
Author(s)
DOI
922311B002104
Abstract
The head kidney of bony fish is composed of
chromaffin cells (similar to mammalian adrenal
medulla), interrenal (similar to mammalian
adrenal cortex), immune tissue and
hematopoietic tissue (similar to mammalian
bone marrow). We have studied secretory
proteins from head kidney for some years and
found that one of the secreted proteins is a
zinc-metalloproteinase. We have successfully
purified this zinc-metalloproteinase and also
isolated one cDNA encoding this protein. Due
to the discrete tissue distribution, we named this
zinc-metalloproteinase as nephrosin. Nephrosin
is a zinc-metalloproteinase and its activity can
be inhibited by metal chelators. It is present only
in the kidney, head kidney, spleen and gill , all
of which are rich in lymphohematopoietic cells.
From amino acid sequence comparison,
nephrosin belongs to the astacin family. The
astacin family includes crayfish astacin, medaka
hatching enzymes, hydra HMP, Xenopus
BMP-1, Drosophila tolloid and mammalian
meprins. So far, nephrosin is the first member of
this family involved in the immune or
hematopoietic functions.
Recently, we have purified a novel protein
inhibitor of carp nephrosin (p40) from carp kidney.
The nephrosin inhibitor forms a 1:1 tight complex
with nephrosin and thus inhibits the enzyme activity.
Interestingly, nephrosin/inhibitor complex seems to
be present only in the lymphohematopoietic tissues.
For the first time, an endogenous inhibitor of the
astacin family has been identified. Immunoblotting
analysis revealed that a serum protein p65 can be
recognized by the anti-p40 antiserum. Cloning of
cDNA encoding p65 reveals that p40 is derived from
carp fetuin. Mammalian fetuins are involved in
diverse functions; opsonization of cationic
macrophage-deactivating molecules, tyrosine kinase
inhibition of the insulin receptor, osteogenesis and
bone resorption, and neocortex development. It is
believed that some of the function of fetuin is
mediated by putative membrane receptors.
However, little is known about the putative fetuin
receptors. Fetuin is a mammalian fetal protein
present in fetal blood, liver, cerebrospinal fluid, and
cerebral cortex. During the fetal development, it plays an essential role in regulating the tissue
differentiation and transformation, especially in the
nervous system and the osteogenesis. It also
participates in the inflammatory response mediated
by macrophages. It may function as a carrier to bring
anti-inflammatory factors into the macrophages. In
this study, we use mouse lung and spleen in which
macrophages are enriched to purify fetuin binding
proteins by fetuin affinity chromatography. We have
found a group of proteins that bind strongly through
hydrophobic interactions with fetuin. Using
MALI-TOF, and LC-MS/MS spectrometry analysis,
and PCR as well, we isolated partial cDNA
sequences of these binding proteins. After antibody
recognition, three molecules were identified as the
putative binding proteins, ubiquinol-cytochrome C
reductase complex core protein 2, mitochondrial
inner membrane protein（IMMT）and alpha 3 B chain
of laminin-5. The first two molecules are resided in
the mitochondrial inner membrane and the third one
is an ECM protein. The physiological significance of
the interactions between fetuin and the three
molecules is needed to be further elucidated.
Subjects
Nephrosin
nephrosin inhibitor
fetuin
metalloproteinase
receptor
Publisher
臺北市：國立臺灣大學生化科學研究所
Type
report
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