Testican is a type of
proteoglycan
Proteoglycans are proteins that are heavily glycosylated. The basic proteoglycan unit consists of a "core protein" with one or more covalently attached glycosaminoglycan (GAG) chain(s). The point of attachment is a serine (Ser) residue to w ...
. Testican-1 is a highly conserved, multidomain proteoglycan that is most prominently expressed in the
thalamus
The thalamus (: thalami; from Greek language, Greek Wikt:θάλαμος, θάλαμος, "chamber") is a large mass of gray matter on the lateral wall of the third ventricle forming the wikt:dorsal, dorsal part of the diencephalon (a division of ...
, and is upregulated in activated
astroglial cells of the cerebrum. Several functions of this gene product have now been demonstrated in
vitro
Vitro is the largest glass producer in Mexico and one of the world's largest organizations in the glass industry. Founded in 1909 in Monterrey, Mexico, this corporation has 30 subsidiaries in Mexico, United States, Brazil, Colombia, Bolivia, Cost ...
including membrane-type matrix
metalloproteinase
A metalloproteinase, or metalloprotease, is any protease enzyme whose catalytic mechanism involves a metal. An example is ADAM12 which plays a significant role in the fusion of muscle cells during embryo development, in a process known as myoge ...
inhibition,
cathepsin L inhibition, and low-affinity calcium binding. The purified gene product has been shown to inhibit cell attachment and neurite extensions in culture. Functions of testican in vivo have yet to be demonstrated in knockout mice or other models. Testican has been shown to carry substantial amounts of
chondroitin
A chondroitin is a chondrin derivative.
Types include:
* Chondroitin sulfate
* Dermatan sulfate
Chondroitin as a supplement is now commonly used (often in combination with glucosamine) in treating the joint disease of osteoarthritis. In contra ...
sulfate as well as other
oligosaccharides
An oligosaccharide (; ) is a saccharide polymer containing a small number (typically three to ten) of monosaccharides (simple sugars). Oligosaccharides can have many functions including cell recognition and cell adhesion.
They are normally presen ...
, but the biological significance of these embellishments is not yet known.
In humans there are three testicans:
*
SPOCK1 (Testican 1)
*
SPOCK2 (Testican 2)
*
SPOCK3 (Testican 3)
Testican-1 plays a role in lapatinib resistance, which is a drug used to treat HER2-positive gastric cancer.
When testican-1 levels are artificially reduced, sensitivity towards lapatinib was once again increased.
This shows the potential for future use in combating drug resistance.
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