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Advancing Understanding of Protein Interactions in Non-Model Organisms

New framework aids in predicting protein interactions, especially for corals.

― 6 min read


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Understanding how proteins interact within living organisms is essential for studying life itself. These interactions help scientists learn about how genes and proteins work together to perform various biological functions. However, most research focuses on well-studied organisms like humans and a few model species, which leaves many non-model organisms poorly explored. This gap in knowledge can hinder efforts to address biological challenges, especially in vital ecosystems like coral reefs.

The Challenge of Protein-Protein Interactions

Scientists have built extensive databases to catalog known protein interactions. These databases, like STRING and BioGRID, compile information from experiments that detail how proteins interact in various organisms. Researchers often use these databases to infer biological functions and relationships among genes. However, the majority of the data in these databases come from humans and a handful of model organisms, making it difficult to apply this knowledge to the vast number of other species.

In many non-model organisms, such as corals, experimental data regarding protein interactions is scarce. This lack of data means that useful networks of interactions cannot be easily established. Since proteins can behave differently even in closely related species, it becomes challenging to use existing data to predict interactions in non-model organisms. Traditional methods also struggle to provide accurate predictions across the broad diversity of life.

Introducing a New Framework: PHILHARMONIC

To address these challenges, a new bioinformatics framework called PHILHARMONIC was developed. This method focuses on non-model organisms, including corals and other species with limited existing data. PHILHARMONIC aims to predict protein interactions and assign biological functions effectively, even when experimental data is lacking.

The key idea behind PHILHARMONIC is that while the predictions made using computer methods may not be perfect, they still contain valuable insights. By refining these predictions through advanced processing techniques, PHILHARMONIC can help create detailed functional networks that researchers can use to better understand the biology of non-model organisms.

How PHILHARMONIC Works

PHILHARMONIC consists of four main steps. First, it employs a Deep Learning method named D-SCRIPT to generate an initial protein-protein interaction network. This network is often noisy, containing many potential false positives and inaccuracies.

Next, a novel clustering algorithm is applied. This algorithm groups proteins into clusters based on their interaction patterns while ensuring that the clusters are manageable in size for biological analysis. In this step, proteins are grouped in a way that allows researchers to examine their functions in more detail.

The third step introduces a method called ReCIPE, which reconnects clusters to improve connectivity among proteins. This process ensures that proteins that naturally belong together in biological terms are more likely to be clustered together, despite being separated in the initial steps.

Finally, PHILHARMONIC uses additional methods to annotate the functions of proteins within these clusters. By employing techniques that analyze gene sequences and known functional roles, PHILHARMONIC can assign biological meanings to uncharacterized proteins based on their relationships with better-known proteins.

Application to Coral Proteomes

Coral reefs are tremendously important ecosystems, hosting a rich diversity of marine life. However, they face various threats, including pollution and climate change. Studying coral biology is essential for developing strategies to protect these environments. Unfortunately, the distance between corals and well-annotated species makes functional studies particularly challenging.

Using PHILHARMONIC, researchers focused on the coral species Pocillopora damicornis and its associated algae. By applying the framework, researchers could predict functional labels for numerous previously uncharacterized proteins. This prediction sheds light on clusters of proteins involved in crucial functions for coral survival-such as temperature sensing and responding to environmental stimuli.

The Importance of Functional Clusters

In biological research, identifying groups of proteins with similar functions is vital. These clusters allow scientists to understand the interconnected roles proteins play within cells. PHILHARMONIC’s clustering approach results in non-overlapping groups that emphasize functional relationships.

However, since proteins can serve multiple roles, the algorithm also allows for flexibility. The ReCIPE method reconnects previously isolated proteins, creating more cohesive and interpretable clusters. This process enhances the biological relevance of the clusters, making them easier for researchers to analyze.

Validating PHILHARMONIC

To ensure the predictions made by PHILHARMONIC are meaningful, the results must be validated. This involves comparing clusters generated by PHILHARMONIC against known functional data. By examining the coherence of the clusters-how well the functions assigned to proteins agree with each other-researchers can assess accuracy.

Using data from corals, scientists found that the clusters generated by PHILHARMONIC exhibited remarkable functional coherence. This means that the proteins within a cluster tended to share similar biological roles, providing confidence in the predictive abilities of the framework.

Moreover, the clusters were found to correlate with Gene Expression data. This indicates that the proteins grouped together by PHILHARMONIC are likely to be active simultaneously within certain conditions, supporting the idea that these clusters reflect real biological processes.

Applications Beyond Corals

While corals present a compelling case study, PHILHARMONIC is not limited to marine biology. The framework was also tested on other organisms, such as the fruit fly. The results showed that PHILHARMONIC could successfully identify enriched functional clusters for these well-studied species, illustrating its versatility.

The ability to apply this framework to different organisms opens the door to new research opportunities. By enabling researchers to analyze proteins in non-model organisms, PHILHARMONIC contributes to a broader understanding of biological systems.

The Potential of Functional Genomics

As PHILHARMONIC facilitates the exploration of functional genomics in non-model organisms, it has the potential to reveal new biological insights. These insights can lead to improved strategies for conservation efforts, particularly in vulnerable ecosystems like coral reefs. By understanding the interactions at play within these systems, scientists can propose actionable solutions to address the threats facing these environments.

In the future, as more genomic data become available and computational methods advance, the potential for PHILHARMONIC and similar frameworks to drive discoveries will continue to expand.

Conclusion

The development of PHILHARMONIC represents a significant step forward in the study of protein-protein interactions in non-model organisms. By harnessing advanced computational techniques, researchers can now predict functional relationships that were previously difficult to ascertain.

With applications in marine biology and beyond, this framework can help bridge the gap in our understanding of diverse biological systems. As we strive to protect and conserve our natural world, tools like PHILHARMONIC will be crucial in guiding our efforts and expanding our knowledge of life on Earth.

Original Source

Title: Decoding the Functional Interactome of Non-Model Organisms with PHILHARMONIC

Abstract: Protein-protein interaction (PPI) networks are a fundamental resource for modeling cellular and molecular function, and a large and sophisticated toolbox has been developed to leverage their structure and topological organization to predict the functional roles of under-studied genes, proteins, and pathways. However, the overwhelming majority of experimentally-determined interactions from which such networks are constructed come from a small number of well-studied model organisms. Indeed, most species lack even a single experimentally-determined interaction in these databases, much less a network to enable the analysis of cellular function, and methods for computational PPI prediction are too noisy to apply directly. We introduce PHILHARMONIC, a novel computational approach that couples deep learning de novo network inference with robust unsupervised spectral clustering algorithms to uncover functional relationships and high-level organization in non-model organisms. Our clustering approach allows us to de-noise the predicted network, producing highly informative functional modules. We also develop a novel algorithm called ReCIPE, which aims to reconnect disconnected clusters, increasing functional enrichment and biological interpretability. We perform remote homology-based functional annotation by leveraging hmmscan and GODomainMiner to assign initial functions to proteins at large evolutionary distances. Our clusters enable us to newly assign functions to uncharacterized proteins through "function by association." We demonstrate the ability of PHILHARMONIC to recover clusters with significant functional coherence in the reef-building coral P. damicornis, its algal symbiont C. goreaui, and the well-annotated fruit fly D. melanogaster. We perform a deeper analysis of the P. damicornis network, where we show that PHILHARMONIC clusters correlate strongly with gene co-expression and investigate several clusters that participate in temperature regulation in the coral, including the first putative functional annotation of several previously uncharacterized proteins. Easy to run end-to-end and requiring only a sequenced proteome, PHILHARMONIC is an engine for biological hypothesis generation and discovery in non-model organisms. PHILHARMONIC is available at https://github.com/samsledje/philharmonic

Authors: Samuel Sledzieski, C. Versavel, R. Singh, F. Ocitti, K. Devkota, L. Kumar, P. Shpilker, L. Roger, J. Yang, N. Lewinski, H. M. Putnam, B. Berger, J. Klein-Seetharaman, L. Cowen

Last Update: 2024-10-29 00:00:00

Language: English

Source URL: https://www.biorxiv.org/content/10.1101/2024.10.25.620267

Source PDF: https://www.biorxiv.org/content/10.1101/2024.10.25.620267.full.pdf

Licence: https://creativecommons.org/licenses/by/4.0/

Changes: This summary was created with assistance from AI and may have inaccuracies. For accurate information, please refer to the original source documents linked here.

Thank you to biorxiv for use of its open access interoperability.

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