Study reveals a novel activation mechanism for Ste2

  • March 16, 2022
Study reveals a novel activation mechanism for Ste2

Vaithish Velazhahan is first author of a Nature paper on the GPCR Ste2, with important implications for treating fungal diseases.

A Gates Cambridge Scholar has shed new light on an important G protein-coupled receptor [GPCR] which could help researchers to better understand and treat fungal diseases such as candidiasis and pulmonary aspergillosis.

GPCRs are membrane proteins which are essential for signal transduction and communicating with an organism’s surrounding environment. GPCRs are divided into six classes (A-F); Class D GPCRs are found exclusively in fungi and regulate fungal survival and reproduction.

Previous research by Gates Cambridge Scholar Vaithish Velazhahan [2018] determined the first ever structure of a fungal GPCR, using Ste2, a prototypical Class D1 GPCR which is essential for mating in the yeast Saccharomyces cerevisiae. Ste2 was found to form a homodimer and couple to two G proteins simultaneously, which provided the first insights into how a transmembrane-mediated GPCR dimer could form and interact with G proteins.

Vaithish, who is doing his PhD in Biological Science at the MRC Laboratory of Molecular Biology, is first author on a new paper, published in Nature, which takes that research forward and shows that Ste2 has a novel method of activation which is unique from mammalian GPCRs.

To capture Ste2 in its various conformations along the activation pathway, Vaithish used different peptide ligands, purifying the GPCR separately under each condition. To purify ligand-free Ste2, Vaithish developed a method called pre-stabilisation of a GPCR by weak association (PSGWAY). This method involves adding a purified wild type heterotrimeric protein, Gpa1-Ste4-Ste18, to help stabilise ligand-free Ste2 before its purification. Then electron cryomicroscopy (cryo-EM) was used to collect multiple datasets of different samples, involving over 32,000 micrographs in total.

Computational processing of the datasets led to the determination of four new Ste2 structures: a ligand-free state, an antagonist-bound state and two agonist-bound intermediate states. Their research highlights that Ste2 has a structural and activation mechanism distinct from all previously determined monomeric GPCRs.

Molecular dynamics simulations were then performed using these structures and revealed allosteric communication pipelines that differed between the various states. The study suggests ways in which allosteric communication within Ste2 may affect their activation which is also relevant to understanding allosteric communication across other transmembrane-mediated GPCR dimers in humans.

The research could have important implications as fungal diseases, such as invasive candidiasis and pulmonary aspergillosis, account for a major disease burden worldwide and cause life-threatening conditions in humans. In addition, they can threaten global food supply through crop infection. An improved understanding of fungal GPCRs can help to tackle these issues.

Due to their wide-ranging cellular functions, GPCRs are also critical to drug development, with approximately one third of all FDA-approved drugs targeting them. Understanding the activation method of Ste2 could encourage new possibilities for rational drug design. More specifically, the research may make it possible to specifically target fungal GPCR signalling without also inadvertently targeting human GPCRs. The researchers say such a fungal-specific means of drug development could help design medicines which avoid off-target effects and possible therapeutic side-effects.

The research was funded by UKRI MRC, the Gates Cambridge Trust and the National Institutes of Health.

Latest News

Towards a dictionary of the human genome

Marie Brunet’s research focuses on the secrets still hidden in our genomes. She says that despite the fact that we live in an era where getting our genome sequenced is possible, we still don’t know the origin of two fifths of inherited diseases. That is because, as she says, the genome only currently maps the […]

Scholar recognised for research into misinformation

A Gates Cambridge Scholar has been shortlisted for a Women of the Future Award for her research into countering misinformation. Melisa Basol [2018] was shortlisted for the science category of the UK Awards which recognises “truly remarkable female scientists, forging new ground in research and scientific achievement”. There are 11 other categories and three special […]

Scholars join forces on anti-cancer drug

Two Gates Cambridge Scholars have joined forces to work on a drug candidate that has the potential to replace one of the most widely used cancer drugs around the world. Dr Anand Jeyasekharan [2004], who did his PhD in Oncology, and Dr Chandler Robinson [2009] who did an MBA at Cambridge, will collaborate on a […]

Making the experiences of imprisoned women activists visible

Growing up in a small town in Bengal, Jigisha Bhattacharya [2022] developed a particular sensitivity to marginalised groups and conflicts between different communities and identities from an early age.  It is this interest and her experience of political protests at university, combined with a longstanding curiosity about the links between politics and the arts, that […]