This Key Event Relationship is licensed under the Creative Commons BY-SA license. This license allows reusers to distribute, remix, adapt, and build upon the material in any medium or format, so long as attribution is given to the creator. The license allows for commercial use. If you remix, adapt, or build upon the material, you must license the modified material under identical terms.

Relationship: 2809

Title

A descriptive phrase which clearly defines the two KEs being considered and the sequential relationship between them (i.e., which is upstream, and which is downstream). More help

Energy Deposition leads to Modified Proteins

Upstream event

The causing Key Event (KE) in a Key Event Relationship (KER). More help

Energy Deposition

Downstream event

The responding Key Event (KE) in a Key Event Relationship (KER). More help

Modified Proteins

Key Event Relationship Overview

The utility of AOPs for regulatory application is defined, to a large extent, by the confidence and precision with which they facilitate extrapolation of data measured at low levels of biological organisation to predicted outcomes at higher levels of organisation and the extent to which they can link biological effect measurements to their specific causes.Within the AOP framework, the predictive relationships that facilitate extrapolation are represented by the KERs. Consequently, the overall WoE for an AOP is a reflection in part, of the level of confidence in the underlying series of KERs it encompasses. Therefore, describing the KERs in an AOP involves assembling and organising the types of information and evidence that defines the scientific basis for inferring the probable change in, or state of, a downstream KE from the known or measured state of an upstream KE. More help

AOPs Referencing Relationship

AOP Name	Adjacency	Weight of Evidence	Quantitative Understanding	Point of Contact	Author Status	OECD Status
Deposition of energy leading to occurrence of cataracts	adjacent	Moderate	Moderate	Arthur Author (send email)	Open for citation & comment

Taxonomic Applicability

Latin or common names of a species or broader taxonomic grouping (e.g., class, order, family) that help to define the biological applicability domain of the KER.In general, this will be dictated by the more restrictive of the two KEs being linked together by the KER. More help

Term	Scientific Term	Evidence	Link
human	Homo sapiens	Moderate	NCBI
rat	Rattus norvegicus	High	NCBI
mouse	Mus musculus	Moderate	NCBI

Sex Applicability

An indication of the the relevant sex for this KER. More help

Sex	Evidence
Unspecific	High

Life Stage Applicability

An indication of the the relevant life stage(s) for this KER. More help

Term	Evidence
All life stages	High

Key Event Relationship Description

Provides a concise overview of the information given below as well as addressing details that aren’t inherent in the description of the KEs themselves. More help

Energy deposition, such as that released from radiation in sensitive lens cells can lead to protein modifications such as disulfide bond formation, D-Asp formation, and carbonylation, among other changes (Hamada et al., 2014; Lipman et al., 1988; Reisz et al., 2014). The modifications arise as energy deposited onto a cell interacts with molecules (e.g. proteins, lipids, DNA), altering the redox balance of the cell, and resulting in amino acid modifications (Neves-Petersen et al., 2012). These changes cause structural and functional molecular-level damage to the proteins, such as aggregation (Reisz et al., 2014; Hamada et al., 2014).

Under homeostatic conditions, cells inherently have a set amount of total protein that are soluble (Pace et al., 2004). These properties can be disrupted by the deposition of energy. The interaction of a soluble protein with large amounts of energy can change its molecular weight and solubility through deamidation and the formation of disulfide bonds (Hanson et al., 2000; Reddy 1990; Miesbauer et al., 1994).

Other types of protein modification can also occur, including protein carbonylation and D-Asp formation (Reisz et al., 2014; Hamada et al., 2014). Protein carbonylation, a result of reactive oxygen species (ROS), is the post-translational addition of carbonyl to the protein’s side chain, these can observably be increased when a cell is exposed to ionizing radiation (Resiz et al., 2014). Inversion of amino acids from the L to D conformation can also occur in response to the ionization events or thermal energy released from radiation, this contributes to protein quaternary structure changes (Fujii et al., 2004).

Evidence Collection Strategy

Include a description of the approach for identification and assembly of the evidence base for the KER. For evidence identification, include, for example, a description of the sources and dates of information consulted including expert knowledge, databases searched and associated search terms/strings. Include also a description of study screening criteria and methodology, study quality assessment considerations, the data extraction strategy and links to any repositories/databases of relevant references.Tabular summaries and links to relevant supporting documentation are encouraged, wherever possible. More help

The strategy for collating the evidence to support the relationship is described in Kozbenko et al 2022. Briefly, a scoping review methodology was used to prioritize studies based on a population, exposure, outcome, endpoint statement.

Evidence Map 2.0

ID	Experimental Design	Species	Upstream Observation	Downstream Observation	Citation (first author, year)	Notes

Evidence Map

Addresses the scientific evidence supporting KERs in an AOP setting the stage for overall assessment of the AOP. More help

Title	First Author	Biological Plausibility	Dose Concordance	Temporal Concordance	Incidence Concordance

Biological Plausibility

Dose Concordance Evidence

Temporal Concordance Evidence

Incidence Concordance Evidence

Uncertainties and Inconsistencies

Addresses inconsistencies or uncertainties in the relationship including the identification of experimental details that may explain apparent deviations from the expected patterns of concordance. More help

Although the relationship is well- supported, the degree and type of modification can be variable depending on the exposure conditions. Significant increases in oxidized crystallin protein are seen anywhere from 5 Gy in vivo (Kim et al. 2015) to 50 Gy in vivo (Kim et al., 2016) to 270 Gy in vitro (Finley et al., 1998). This relationship is difficult to predict.

Known modulating factors

This table captures specific information on the MF, its properties, how it affects the KER and respective references.1.) What is the modulating factor? Name the factor for which solid evidence exists that it influences this KER. Examples: age, sex, genotype, diet 2.) Details of this modulating factor. Specify which features of this MF are relevant for this KER. Examples: a specific age range or a specific biological age (defined by...); a specific gene mutation or variant, a specific nutrient (deficit or surplus); a sex-specific homone; a certain threshold value (e.g. serum levels of a chemical above...) 3.) Description of how this modulating factor affects this KER. Describe the provable modification of the KER (also quantitatively, if known). Examples: increase or decrease of the magnitude of effect (by a factor of...); change of the time-course of the effect (onset delay by...); alteration of the probability of the effect; increase or decrease of the sensitivity of the downstream effect (by a factor of...) 4.) Provision of supporting scientific evidence for an effect of this MF on this KER. Give a list of references. More help

Modulating Factor (MF)	MF Specification	Effect(s) on the KER	Reference(s)
Age	The absorption of radiation in the lens of the eye, such as UV, increases with age.	Free UV filters exist in the eye to help block UV from interacting with proteins in the lens. The filters, such as tryptophan metabolites, degrade as people age, reducing the protection for proteins in the lens.	Bron et al., 2000; Davies & Truscott, 2001; Truscott & Friedrich, 2016
Free Radical Scavengers	The addition of antioxidants attenuates the effect of energy deposition.	Sodium Azide (NaN₃) and Cystamine, free radical scavengers, reduce the amount of cross-linking of crystalline proteins.	Zigler & Goosey, 1981; Shin et al., 2004

Quantitative Understanding of the Linkage

Captures information that helps to define how much change in the upstream KE, and/or for how long, is needed to elicit a detectable and defined change in the downstream KE. More help

The following tables provide representative examples of the relationship, unless otherwise indicated, all data is significantly significant.

Dose Concordance

Reference	Experiment Description	Result
Abdelkawi et al., 2008	In vivo, two-month-old adult male Swiss albino mice received whole-body radon exposure to 3.54 mJ m^-3 h for six continuous weeks (dose of 637.2 mJ m^-3) and the levels of soluble protein were measured using a Lowry assay.	Cells showed a decrease in soluble lens protein concentration (indicative of increased protein modification) to 0.85x control.
Abdelkwai, 2012	In vivo, rats received whole-body exposure to 0.5 Gy/week of γ-rays and observed identified molecular weight changes in proteins using spectroscopy.	Cells showed an increase in crystallin molecular weight with each isoform, α, β-H, β-L, and γ increasing 28, 16, 27, and 54% relative to control.
Kim et al., 2015	In vitro, rat lenses exposed to 2.8 Gy/h γ-ray and protein oxidation was detected using liquid chromatography-tandem mass spectroscopy.	A 5 Gy γ-ray treatment group had 10 sites of oxidation on water-soluble and water-insoluble γE- or γF-crystallin proteins.
Sherif & Abdelkawi, 2006	In vivo, rat lenses received whole-body γ-ray exposure to 0.5 Gy/week and total soluble protein level was determined by the Lowry assay.	Rat lenses exposed to 0 - 4.0 Gy γ-rays showed a decrease in soluble lens protein (indicative of increased modified protein levels) with the maximum dose displaying a 1.6x decrease relative to control.
Shang et al., 1994	In vitro, bovine lens cortices exposed to 0-500 Gy at 3.96 Gy/min γ-rays and protein changes (β- and γ-crystallins) assessed using SDS-PAGE.	Cells exposed to 0-500 Gy displayed a linear increase in β-crystallin fragmentation above 10 Gy. They also displayed increased protein aggregates above 10 Gy, with the notable exception of β-crystallin which exhibited a slight drop below the trend line (but not below control) at 50 Gy.
Anbaraki et al., 2016	In vitro, bovine lens proteins exposed to 316 W/m²UV and protein modifications assessed using SDS-PAGE.	Increased cross-linking and oligomerization of UV-exposed lens proteins was observed Increase in dose caused an increase in higher molecular weight proteins, starting at 0.5 hr of light exposure, with another increase at 2 hrs of light. The non-native staining is relatively similar for 2-4hr exposures, but with increase dose, native staining decreases
Zigler & Goosey, 1981	In vitro, human lens proteins exposed to 12.5 W/m² UV and protein modification was detected using SDS-PAGE.	24 h exposure to UV resulted in increased molecular weight of crystallin proteins. This trend continued with the 48hr dose group.
Andley et al., 1990	In vitro, rabbit lens epithelial cells exposed to 70 or 140 Jm^-2 UVB and protein modifications assayed via SDS-PAGE and autoradiographic scans.	UVB irradiation caused a decrease in the amount of 37 kD protein that was produced and expelled from the cells. Exposure to 70 J/m² led to a 7% decrease in 37 kD protein levels and exposure to 140 J/m² led to a 50% decrease in 37 kD protein levels. However, most of the other proteins remained unchanged.
Moran et al., 2013	In vitro, human crystallins exposed to 35 W/m² UVB for 6 h and protein weight changes detected using SDS-PAGE.	Exposure to 35 Wm-2 UVB for 6 h results in increased concentration of γD-crystallin proteins above 20 kDa molecular weight compared to control.
Fochler & Durchschlag, 1997	In vitro, calf crystallins exposed to UV (60, 100, 150 kJ/m2) or X-rays (1, 5, 10 kGy). Changes in protein weight were detected using SDS-PAGE.	At all doses measured, there is either a shift or a disappearance of the alpha and gamma crystallins on the SDS-PAGE.
Zigman et al., 1975	In vivo, mice received whole-body exposure to 450 μW/cm² long-wave UV and insoluble protein level was assessed using SDS-PAGE.	At 4 weeks of UV (12 hr on/off cycle), the treatment group and the control group were shown to diverge with a linear increase in the treatment group. At 8 weeks of UV (12 hr on/off cycle), the treatment group reached an insoluble protein level of 0.35 mg/lens, 1.4x control level.
Giblin et al., 2002	In vivo, guinea pigs received whole-body exposure to 0.5 mW/cm² UVA and protein solubility changes were measured using the BCA protein assay.	Lens nucleus cells exposed to 4-5 months of UV-A had 276 mg/g water-soluble protein level. This is 20% less than the 343 mg/g seen in control groups. The cortex did not have significant differences.
Simpanya et al., 2008	In vivo, guinea pigs received whole-body exposure to 0.5 mW/cm² UVA and protein changes were assayed using dynamic light scattering.	After 5 months exposure to UV-A, proteins in the nucleus had a higher average diameter compared to control. At 2.1 mm across the optical axis, the UV group had an average of 1020 diameter (arbitrary units), 5.67x the control's 180 average.

Time Concordance

No evidence found.

Response-response Relationship

Provides sources of data that define the response-response relationships between the KEs. More help

Time-scale

Information regarding the approximate time-scale of the changes in KEdownstream relative to changes in KEupstream (i.e., do effects on KEdownstream lag those on KEupstream by seconds, minutes, hours, or days?). More help

Known Feedforward/Feedback loops influencing this KER

Define whether there are known positive or negative feedback mechanisms involved and what is understood about their time-course and homeostatic limits. More help

N/A

Domain of Applicability

A free-text section of the KER description that the developers can use to explain their rationale for the taxonomic, life stage, or sex applicability structured terms. More help

This KER is plausible in all life stages, sexes, and organisms. The majority of the evidence is from in vivo male adult rats, and in vitro bovine models that do not specify sex.