Promoting Receptor Protein Tyrosine Phosphatase Activity by Targeting Transmembrane Domain Interactions - Below is the original Project Summary to fill this mandatory field
Receptor protein tyrosine phosphatases (RPTPs) play critical signaling regulatory roles in development,
health, and disease progression. Despite the clear importance of RPTPs in signal transduction, very little is
known about the structure-function relationships that underpin the regulation of their activity. The reported
ability of RPTP homodimerization to antagonize their catalytic activity, however, presents potential
opportunities to develop strategies to promote RPTP activity against their oncogenic receptor tyrosine kinase
(RTK) substrates. We recently showed, using PTPRJ/EGFR as a model RPTP/RTK pair, that: (i)
homodimerization of PTPRJ (also known as DEP1) is regulated by transmembrane domain interactions, and
(ii) disrupting these interactions can antagonize PTPRJ homodimerization, reduce substrate EGFR
phosphorylation, and antagonize EGFR-driven cell phenotypes.
Here, we propose to build upon these new insights along three thematically interconnected, but non-
overlapping, specific aims, with the ultimate goals of: (1) demonstrating that RPTP TM domain interactions are
essential in regulating their activity and substrate access, and (2) developing a new therapeutic approach to
promote RPTP activity against their oncogenic RTK substrates.
In our first aim, we will determine the molecular determinants regulating the heterodimerization of PTPRJ with
EGFR. These studies will be complemented by extending them to understand how PTPRJ TM domain mutants
affect receptor trafficking and ultimate cell outcomes. In the second aim, we will design and select peptides
capable of binding to PTPRJ TM domains and test their ability to disrupt PTPRJ homodimerization, promote
PTPRJ activity against EGFR and other substrate RTKs, and selectively target human tumor xenografts in
mice. In the third aim, we will identify other candidate RTK substrates whose regulation by PTPRJ depends
upon TM domain-mediated heterodimerization, and determine how different cellular contexts predict the cell
signaling and phenotype outcome of interfering with PTPRJ dimerization through TM domains. To do so, we
will implement a systems biology approach based on data-driven computational modeling of phenotypic
measurements and global mass spectrometry measurements of protein phosphorylation and expression in a
panel of cell lines. This aim is motivated by an understanding that all RPTPs have multiple substrates and that
variations in expression of those substrates among cells may lead to different outcomes when PTPRJ
dimerization is disrupted.
Ultimately, the studies proposed here stand to advance both our basic biological understanding of RPTP
biology, which is critically needed, and to lead to new methods to target signaling through oncogenic RTKs that
may be less susceptible to common mechanisms of acquired resistance to RTK inhibitors.
