ADAMTS10 Regulation of Transforming Growth Factor Beta

Vanderbilt University Medical Center, Nashville TN

Investigators

Abstract

Glaucoma is a leading cause of irreversible blindness due to neurodegeneration of retinal ganglion cells. Previously, we discovered a mutation in the gene encoding the matrix metalloprotease, ADAMTS10, that causes Primary Open Angle Glaucoma (POAG) in a colony of Beagle dogs. This mutation results in a glycine- to-arginine substitution at amino acid 661 (G661R) in the cysteine-rich domain that may disrupt a protein interaction surface. Our discovery was verified with the finding of an A387T mutation in the catalytic domain of ADAMTS10 that causes POAG in Norwegian Elkhounds. To investigate the pathogenic mechanisms of glaucoma-causing ADAMTS10 mutations, we created mouse lines carrying either the G661R or the A387T mutation of Adamts10. We found that mice homozygous for the G661R mutation displayed reduced TGFβ signaling in the developing inner retina of postnatal day 10 mice which was associated with increased apoptosis. This correlated with reduced RGC axon number and attenuated retinal function in adult mice. These findings suggest the hypothesis that glaucoma-causing mutations of Adamts10 reduce neuroprotective TGFβ signaling in the developing retina resulting in optic nerve and retinal pathology in the adult. We also discovered direct interaction between ADAMTS10 and the latency associated peptide of TGFβ, suggesting the hypothesis that ADAMTS10 directly regulates TGFβ. A similar direct regulatory mechanism has been shown for two other ADAMTS family members, ADAMTS1 and ADAMTS16. In this mechanism, interactions between the cysteine rich domain of the ADAMTS and the latency associated peptide of TGFβ allow interaction of TGFβ and its receptor, activating TGFβ signaling. We will make use our mutant Adamts10 mouse lines to accomplish the following: Specific Aim 1: Define the mechanism by which ADAMTS10 promotes TGFβ signaling. Our finding of direct interaction between ADAMTS10 and TGFβ-LAP suggest a direct regulatory mechanism as has been shown for ADAMTS1 and ADAMTS16. The mechanism of promoting TGFβ signaling and the effects of glaucoma-causing mutations of ADAMTS10 will be investigated by cell culture transfection approaches. Specific Aim 2: Test the hypothesis that reduced TGFβ signaling results in development of fewer optic nerve axons in adult G661R and A387T mice. Glaucoma-causative mutations of Adamts10 reduce TGFβ signaling in developing ganglion cell layer of the retina which results in reduced RGC function and axon number in adult mice. TGFβ signaling in the ganglion cell layer of the retina in P4 – P10 mice will be experimentally reduced by disruption of ADAMTS10/TGFβ-LAP interaction and by treatment with losartan of postnatal mice. Mice will be matured to adults and RGC function and optic nerve axon counts determined. Significance: Confirmation of our hypotheses would suggest that direct regulation of TGFβ signaling is a common feature of the ADAMTS family. Since this interaction can be manipulated by exogenous peptides, this may offer novel approaches to alter TGFβ signaling as a treatment for glaucoma and other diseases.