Different Grp94 components interact transiently with the myocilin olfactomedin domain in vitro to enhance or retard its amyloid aggregation

Huard, D.J.E.; Jonke, Alex P.; Torres, Matthew P.; Lieberman, Raquel L.

doi:10.1038/s41598-019-48751-8

Cited by 13 publications

(11 citation statements)

References 61 publications

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“…BiP suppresses oligomerization while Grp94 enhances oligomerization (Figure 5). Our findings with Grp94 and proIGF2 are consistent with reports that Grp94 enhances the self-association of the secreted protein myocilin 53 . We find that Grp94 enhances proIGF2 oligomerization by increasing the assembly rate (k+ in Figure 6) rather than from slowing the transition into irreversible aggregates.…”

Section: Discussionsupporting

confidence: 93%

The ER Chaperones BiP and Grp94 Regulate the Formation of Insulin-Like Growth Factor 2 (IGF2) Oligomers

Jin

Kotler

Wang

et al. 2021

Journal of Molecular Biology

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While cytosolic Hsp70 and Hsp90 chaperones have been extensively studied, less is known about how the ER Hsp70 and Hsp90 paralogs (BiP and Grp94) recognize clients and influence their folding. Here, we examine how BiP and Grp94 influence the folding of insulin-like growth factor 2 (IGF2). Full-length proIGF2 is composed of an insulin-like hormone and an E-peptide that has sequence characteristics of an intrinsically disordered region. We find that the E-peptide region allows proIGF2 to form oligomers. BiP and Grp94 influence both the folding and the oligomerization of proIGF2. BiP and Grp94 exert a similar holdase function on proIGF2 folding by preferentially binding the proIGF2 unfolded state, rather than stabilizing specific folding intermediates and changing the proIGF2 folding process. In contrast, BiP and Grp94 exert counteracting effects on proIGF2 oligomerization. BiP suppresses proIGF2 oligomerization under both ADP and ATP conditions. Interestingly, Grp94 can enhance proIGF2 oligomerization whenGrp94 adopts an open conformation (ADP conditions), but not when Grp94 is in the closed conformation (ATP conditions). We propose that BiP and Grp94 regulate the assembly of proIGF2 oligomers, and that regulated oligomerization may enable proIGF2 to be effectively packaged for export from the ER to the Golgi.

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Section: Discussionsupporting

confidence: 93%

The ER Chaperones BiP and Grp94 Regulate the Formation of Insulin-Like Growth Factor 2 (IGF2) Oligomers

Jin

Kotler

Wang

et al. 2021

Journal of Molecular Biology

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“…Gln368* and likely other mid-OLF termination variants share laboratory characteristics of missense variants: the intracellular deposits (Gobeil et al, 2006) exhibit a dominant negative effect with respect to WT myocilin (Gobeil et al, 2004) and are insoluble in Triton X-100 (Shimizu et al, 2000). Such nonfolding termination variants would likely not reach the stage of protein quality control involving Grp94 (Huard et al, 2019(Huard et al, , 2018Marzec et al, 2012;Stothert et al, 2014;Suntharalingam et al, 2012) and thus be identified by different ER chaperones (Ellgaard et al, 2016), leading to different consequences. Further laboratory investigations of termination variants would be informative.…”

Section: Uncertain Significancementioning

confidence: 99%

Common and rare myocilin variants: Predicting glaucoma pathogenicity based on genetics, clinical, and laboratory misfolding data

et al. 2021

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Rare variants of the olfactomedin domain of myocilin are considered causative for inherited, early-onset open-angle glaucoma, with a misfolding toxic gain-of-function pathogenic mechanism detailed by 20 years of laboratory research. Myocilin variants are documented in the scientific literature and identified through large-scale genetic sequencing projects such as those curated in the Genome Aggregation Database (gnomAD). In the absence of key clinical and laboratory information, however, the pathogenicity of any given variant is not clear, because glaucoma is a heterogeneous and prevalent age-onset disease, and common variants are likely benign. In this review, we reevaluate the likelihood of pathogenicity for the~100 nonsynonymous missense, insertion-deletion, and premature termination of myocilin olfactomedin variants documented in the literature. We integrate available clinical, laboratory cellular, biochemical and biophysical data, the olfactomedin domain structure, and population genetics data from gnomAD. Of the variants inspected,~50% can be binned based on a preponderance of data, leaving many of uncertain pathogenicity that motivate additional studies. Ultimately, the approach of combining metrics from different disciplines will likely resolve outstanding complexities regarding the role of this misfolding-prone protein within the context of a multifactorial and prevalent ocular disease, and pave the way for new precision medicine therapeutics.

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“…Only pharmacological inhibition, which should stabilize Grp94 in its closed state, both reverts aggregation kinetics and rescues coaggregation (Figure 5d,e). 18,32 In support of the proposal that selective inhibition of Grp94 is a viable therapeutic approach for myocilin-associated glaucoma are preliminary in vivo studies in which the Grp94 inhibitor 4-Br-BnIm was administered to a mouse model of myocilin glaucoma, resulting in a reduction of IOP. 43 Our lab has used a medium-throughput screen to identify additional scaffolds for molecules that could rescue Grp94 from coaggregation with mutant myocilin and promote its degradation, 18 with a plan to extend to larger compound libraries.…”

Section: Aggregationmentioning

confidence: 97%

“…The electrostatic surface potential indicates both positively charged and acidic patches on both the top and bottom face of the propeller . mOLF is isolated as a monomer by size-exclusion chromatography and only low levels of dimer are captured by chemical cross-linking, suggesting that intrinsic dimerization is transient or weak. In sum, CC confers the molecular tetramer and LZ serves as molecular spacers: the tetrameric CC diverges into two parallel LZ dimers to form the Y, to which two pairs of the C-terminal mOLF are flexibly connected via the disordered linker (Figure ).…”

Section: Structure Of Wt Myocilinmentioning

confidence: 99%

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Molecular Insights into Myocilin and Its Glaucoma-Causing Misfolded Olfactomedin Domain Variants

Lieberman

Thu

2021

Acc. Chem. Res.

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Metrics & MoreArticle Recommendations CONSPECTUS: Numerous human disorders arise due to the inability of a particular protein to adopt its correct threedimensional structure in the context of the cell, leading to aggregation. A new addition to the list of such protein conformational disorders is the inherited subtype of glaucoma. Different and rare coding mutations in myocilin, found in families throughout the world, are causal for early onset ocular hypertension, a key glaucoma risk factor. Myocilin is expressed at high levels in the trabecular meshwork (TM) extracellular matrix. The TM is the anatomical region of the eye that regulates intraocular pressure, and its dysfunction is associated with most forms of glaucoma. Disease variants, distributed across the 30 kDa olfactomedin domain (mOLF), cause myocilin to be sequestered intracellularly instead of being secreted to the TM extracellular matrix. The working hypothesis is that the intracellular aggregates cause a toxic gain of function: TM cell death is thought to lead to TM matrix dysfunction, hastening elevated intraocular pressure and subsequent vision loss.Our lab has provided molecular underpinnings for myocilin structure and misfolding, placing myocilin-associated glaucoma within the context of amyloid diseases like Alzheimer and diabetes. We have dissected complexities of the modular wild-type (WT) myocilin structure and associated misfolded states. Our data support the model that full-length WT myocilin adopts a Y-shaped dimer-of-dimers conferred by two different coiled-coil regions, generating new hypotheses regarding its mysterious function. The mOLF β-propellers are paired at each tip of the Y. Disease-associated variants aggregate because mOLFs are less stable, leading to facile aggregation under physiological conditions (37 °C, pH 7.2). Mutant myocilin aggregates exhibit numerous characteristics of amyloid in vitro and in cells, and aggregation proceeds from a partially folded state accessed preferentially by disease variants at physiological conditions. Interestingly, destabilization is not a universal consequence of mutation. We identified counterintuitive, stabilizing point variants that adopt a non-native structure and do not aggregate; however, these variants have not been identified in glaucoma patients. An ongoing effort is predicting the consequence of any given mutation. This effort is relevant to interpreting data from large-scale sequencing projects where clinical and family history data are not available. Finally, our work suggests avenues to develop disease-modifying precision medicines for myocilin-associated glaucoma.

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Different Grp94 components interact transiently with the myocilin olfactomedin domain in vitro to enhance or retard its amyloid aggregation

Cited by 13 publications

References 61 publications

The ER Chaperones BiP and Grp94 Regulate the Formation of Insulin-Like Growth Factor 2 (IGF2) Oligomers

The ER Chaperones BiP and Grp94 Regulate the Formation of Insulin-Like Growth Factor 2 (IGF2) Oligomers

Common and rare myocilin variants: Predicting glaucoma pathogenicity based on genetics, clinical, and laboratory misfolding data

Molecular Insights into Myocilin and Its Glaucoma-Causing Misfolded Olfactomedin Domain Variants

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