Download Expression of Ras-GTPase isoforms in rodent and human polycystic

Expression of Ras-GTPase isoforms in rodent and human polycystic kidney disease
Small Ras GTPases act as central mediators for numerous effector cascades and are crucial in
the control of cell proliferation, differentiation and apoptosis. Ras-GTPase signalling has been
implicated in the pathogenesis of polycystic kidney disease (PKD), however the role of the 3
isoforms, Kirsten (Ki)-, Neural (N)- and Harvey (Ha)- Ras, in PKD are unknown.
Our previous work has shown upregulation of Ki- and N-Ras isoforms across the proliferative
and fibrotic phases of disease progression in an orthologous ADPKD mouse model. Here we
extend our studies to examine Ras expression in human polycystic kidneys, and a mouse model
of recessive polycystic kidney disease.
Immunohistochemistry (IHC), qPCR and immunoblotting were used to characterize Ras
expression in normal and human polycystic kidney tissue, and in Pcy mice.
Similar to our findings in a Pkd1nl/nl hypomorphic mouse model, 2-3 fold rises in N- and KiRas mRNA expression occur in Pcy mice compared to wt between weeks 10 to 20, crossing
both proliferative and fibrotic stages of disease (p=<0.05). Interestingly, in this model Ha-Ras
mRNA is also elevated 2-fold during the early phase of cystic development (p=<0.05), declining
after week 10.
In human disease, strong expression of Ras protein is found confined to the epithelia of cysts,
and tubules in both the medulla and cortex of pre-dialysis stage polycystic kidneys (E-PKD),
and end-stage polycystic kidneys (ES-PKD). Phospho-ERK similarly localises to these cells in
human E- and ES-PKD. This cellular pattern of expression mimics our previous findings in the
Pkd1nl/nl mouse model.
These results show a correlation in the cellular localisation of Ras and p-ERK expression
between human ADPKD and PKD mouse models. In addition, a clear pattern of Ki- and N- Ras
upregulation associated with different phases of disease progression occurs in 2 distinct models
of polycystic kidney disease. These data further support a role for Ras-isoforms in PKD
pathogenesis.