Restoring Ocrl1 function in Lowe Syndrome and Dent-2 disease

Lowe Syndrome (LS) is a disease caused by mutations in the OCRL1 gene that unfortunately leads to the
early death of affected children and has no cure. However, this project aims to change such scenario. Further,
since OCRL1 mutations also cause a related renal condition known as Dent-2 (D2) disease, this proposal will
also benefit D2 patients.
LS patients display mental retardation, ocular (e.g., glaucoma, cataracts) and renal (e.g., kidney stones,
LMW proteinuria) abnormalities, while D2 patients show renal symptoms almost exclusively. Although most
OCRL1 missense mutations found in patients alter the phosphatase domain of the encoded protein Ocrl1, about
half of these changes do not affect residues involved in binding or modification of the substrate. In fact, our
results indicate that a substantial number of patients express Ocrl1 mutated proteins with intact binding/catalytic
sequences but locked in a conformation unable to process lipid substrates. Therefore, we HYPOTHESIZE that a
subset of Ocrl1 patient mutated proteins can re-acquire functionality by action of drugs able to stabilize
the enzymatically active conformer (allosteric activators). Indeed, as a result of a series of small molecule
screens performed in our lab, we identified a group of compounds (including FDA-approved drugs) as able to
restore catalytic activity of different Ocrl1 patient mutants and to suppress a readout LS/D2 cellular phenotype.
To test our hypothesis, 4 allosteric activator candidates will be used along with a panel of LS and D2 Ocrl1
patient mutated variants to pursue the following specific aims focused on kidney function:
AIM 1. To determine the in vitro effect of selected candidate drugs ON THE BIOCHEMICAL ACTIVITY of a panel
of Ocrl1 LS/D2 patient mutated variants.
AIM 2. To determine the effect of selected candidate drugs ON MULTIPLE LS PHENOTYPES observed in kidney
cell lines, kidney organoids and a zebrafish animal model bearing LS/D2 patient OCRL1 mutations.
AIM 3. To determine the effect of selected candidate drugs ON THE STABILITY AND STRUCTURE of the Ocrl1
LS/D2 mutated variants bound or not to substrate.
This project is INNOVATIVE because it introduces the concept of LS and D2 as heterogenous conditions with
some patients displaying a conformational/misfolding disease component and proposes a novel therapeutic
approach using allosteric activators. Importantly, this project has high SIGNIFICANCE as it will address the lack of
therapeutic approaches designed to suppress the upstream cause of a disease that affects tens of thousands of
children in the US and worldwide. Further, FDA-approved candidate drugs currently used to ameliorate other
conditions can be readily repurposed to LS/D2. Therefore, the translational IMPACT of this project is very high.

Grant Number: 5R01DK131049-05
NIH Institute/Center: NIH
Principal Investigator: Ruben Aguilar