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“Lift and Separate”
Urokinase Plasminogen Activator Receptor (uPAR) and Its Role in Metastasis
Nathan Hale High School SMART Team: Karmenleen Bajwa, Ashley Brost, Nick Gonzalez, Sukhwinder
Kaur, Callan Loberg, Joelle Pietrzak, Rachel Pietrzak, Jamie Rypel, Samantha Toth, Kyle Tretow
Teachers: Susan Getzel and Anne Xiong
Mentor: Nancy M. Dahms, Ph.D., Dept. of Biochemistry, Medical College of Wisconsin
Abstract
Cancer is spread by the plasminogen activation system which is
also responsible for biological processes including clearance of
fibrin clots, cell migration, and activation of growth factors. The
key role is played by urokinase plasminogen activator receptor
(uPAR) which is a tethered membrane protein receptor having
three domains, one of which is critical in activating its substrate,
the serine protease urokinase plasminogen activator (uPA). uPA
activation begins when two of uPA’s domains (an N-terminal
growth factor domain (GFD) and a kringle domain) interact with
domain one of uPAR, creating a tight bond which converts uPA
to its active form. The proteolytic cascade reaction continues
when activated uPA converts inactive plasminogen to the active
protease plasmin. Plasmin is a multi-use protease that can
activate several matrix metalloproteinases, which along with
plasmin, leads to digestion of extracellular matrix (ECM) and
enhanced cellular migration. The binding of uPA to uPAR
localizes these proteolytic cascades to the migrating edge of the
cell, thereby clearing a path in the extracellular matrix that the
cells can move through. Tumor cells often express high levels of
uPA and uPAR, facilitating metastasis. uPA-uPAR expression
can change a benign tumor into a malignant tumor. The activity
of uPAR can be regulated by the proteolytic removal of its Nterminal D1 domain. When uPAR’s N-terminal D1 domain is
disabled or removed it cannot bind to uPA, therefore the cancer
cells lack the ability to metastasize. This prevention technique
could lead to the cure for cancer.
Background
A number of factors can cause tumors, including
environmental carcinogens and inherited genetic mutations.
Tumors are classified as either benign or malignant.
Malignant cells have the ability to spread throughout the body
by detaching from the tumor and entering the circulatory
system. When cells in a malignant tumor invade other body
tissues it is referred to as cancer cell metastasis. The cancer
cells deprive other cells of nutrients. Therefore, the cells
cannot function and this will eventually lead to cell death.
Cancer is the result of these processes. Urokinase
plasminogen activator receptor (uPAR) which is
overexpressed in cancer cells, allows a benign tumor to
become malignant by taking part in the digestion of the
extracellular matrix (ECM). Once the ECM is gone, cells are
free to move. Exploration of uPAR’s binding site may help
prevent cancer metastasis.
Deterioration of Extracellular Matrix (ECM) in
Tumor Cells Leads to Cancer Cell Metastasis
ECM Degradation
Intact ECM
B.
Plasmin
Mr x 10-3
A: uPA is
activated after
binding to uPAR.
1
2
3
9467-
uPA and uPAR
43-
The activation of uPA requires the binding of uPAR with domain 1 (D1), in order for uPA to activate
plasminogen. The activation of plasminogen leads to the activation of plasmin, which degrades the ECM.
The inactivation of uPA can be achieved by cleaving D1 from uPAR.
Active:
uPA (gray) bound to
uPAR, mainly through
interactions between the
hydrophobic amino acid
residues (yellow).
uPAR with all three
domains connected. The
binding crevice for uPA can
be seen where the amino
acids are highlighted
(yellow and chartreuse).
Inactive:
uPAR with domain 1 (orange)
cleaved by protease, at the
linker region, from domain 2
(magenta) and domain 3
(green).
30-
uPA and D1
2014-
uPA
Lane 1 is the control showing only uPA.
Lane 2 is uPA bound to uPAR. In lane 3 the
~80 kDa sample is uPA with full length uPAR
only. The ~30 kDa sample in lane 3 is uPA
bound to only domain 1 (D1) of uPAR. Lane
3 shows that uPA must bind to domain 1 in
order for protein interaction to occur.
The amino acid
residues
highlighted in
yellow represent a
hydrophobic area
on both D1
(orange) and uPA
(gray), which
leads to high
binding affinity
between the two.
Conclusion
2fd6.pdb
ECM Absent
2fd6.pdb
Metastasis of a Tumor
C.
Cascade
Reaction
A.
SDS-Page Gel Separation of
D1 from uPAR
The Interaction of uPA and uPAR
Plasminogen
Nathan Hale
2fd6.pdb
Cancer is spread by the plasminogen
activation process which is also
responsible for biological functions
including clearance of fibrin clots, cell
migration, and activation of growth
factors. When uPAR’s N-terminal D1
domain is disabled or removed it cannot
bind to uPA, therefore the cancer cells
lack the ability to metastasize. Applying
this knowledge could lead to the
prevention or treatment of cancer.
References
Behrendt, N., Ploug, M., Patthy, L., Houen, G., Blasi, F., & Dan, K. (1990) The
Ligand-binding Domain of th e Cell Surface Receptor for
Urokinase-type Plasminogen Activator. The Journal of Biological Chemistry, 7842-7847.
B: Proteolytic
C: Disconnected
cascade reaction
cells are free to
begins digestion of metastasize.
ECM
Huai, Q., Mazar, A. P., Kuo, A., Parry, G. C., Shaw, D. E., Callahan, J., & ... Huang, M. (2006). Structure
of Human Urokinase Plasminogen Activator in Complex with Its Receptor. Science, 311(5761), 656-659.
Retrieved from EBSCOhost.
Tumor in situ
Angiogenesis begins
Metastasis
SMART Teams are supported by the National Institutes of Health (NIH)- National Center for Research Resources-Science Education Partnership Award (NCRR-SEPA), and an NIH CTSA Award to the Medical College of Wisconsin.