Bone sialoprotein (BSP) is an
acidic, noncollagenous glycoprotein abundantly bidding in mineralized tissues.
Although BSP is frequently acclimated as a brand of osteoblast differentiation,
the role of the protein in osteoblast action is unclear. BSP belongs to the
SIBLING (Small Integrin-binding LIgand N-linked Glycoprotein) ancestors of
RGD-containing cast proteins, several associates of which accept been apparent
to affect corpuscle differentiation. The accustomed levels of BSP announcement
in osteoblasts were accurately adapted by CMV-mediated adenoviral
overexpression in primary osteoblasts or inhibition by an RNA
interference-based action in the MC3T3E1 corpuscle line. Alternatively,
osteoblast cultures were supplemented with recombinant BSP protein.
Quantitative real-time PCR was acclimated to adviser the mRNA levels of the
osteoblast-related archetype factors Osterix and Runx2 as able-bodied as the
osteoblast-specific gene osteocalcin. As markers of osteoblast differentiation,
acrid phosphatase agitator activity, Runx2-luciferase anchorman action and
calcein assimilation into mineralized cultures were aswell measured. The
overexpression of BSP added osteoblast-related gene announcement as able-bodied
as calcium assimilation and birthmark accumulation by osteoblast cultures.
Similarly, supplementation of osteoblast cultures with recombinant BSP added
several markers of osteoblast differentiation. Conversely, abolishment of BSP
announcement by small-hairpin RNA-encoding plasmids inhibited announcement of
osteoblast markers and birthmark formation. Overexpression of several
functional-domain mutants of BSP approved that increases in osteoblast-related
gene announcement and cast mineralization empiric in BSP overexpression models
are advised by the integrin-binding RGD burden begin abreast the C-terminus of
the protein. These after-effects authenticate that BSP may serve as a
matrix-associated arresting anon announcement osteoblast adverse consistent in
the added assembly of a mineralized matrix.
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