Research projects

Current projects

Honours projects

Ms Alexandra Thompson

BSc (Hons) Human Physiology- Cellular Physiology

Investigation into the regulation of Kiss1R cell surface expression

The kisspeptin receptor, Kiss1R, is a G protein-coupled receptor (GPCR). Activation of Kiss1R by its cognate ligand kisspeptin results in the release of gonadotropin-releasing hormone (GnRH) and subsequent stimulation of the hypothalamic-pituitary-gonadal axis.  This results in gonadal steroidogenesis and the initiation of puberty and maintenance of reproductive functioning in adults. Emerging evidence suggests that the receptor also has an influencing role in metabolism, cancer, and several other physiological systems throughout the body.  Our research focuses on examining the regulation of cell surface expression of receptors, including Kiss1R, in the reproductive-axis.

 

Ms Mandy Naude

BSc (Hons) Human Physiology- Cellular Physiology

Assessment of the toxicity, estrogenic and androgenic activity of various brands of paracetamol and ibuprofen

The presence of various pharmaceuticals in drinking water sources in South Africa has made pharmaceuticals contaminants of emerging concern. Many pharmaceuticals have been found to interfere with the normal biosynthesis and action of hormones by acting as endocrine disrupting chemicals (EDC’s). This project aims at using recombinant yeast assays to screen different brands of paracetamol and ibuprofen for estrogenic and androgenic activity in order to determine if these pharmaceuticals possess endocrine disrupting activity. For more information on EDC’s visit https://endocrinedisruption.org/

 

Mr Robert Reeve

BSc (Hons) Human Cell Biology

Localisation of kisspeptin and neurokinin B receptors in the rat brain and peripheral tissues

The aim of this project is to determine the whole body biodistribution of the kisspeptin and neurokinin B receptors in a rat model. This will be conducted by labelling the natural ligands with a radioactive-isotope, treating the animals with the ligands and thereafter identifying receptor binding sites by the use of a micro-PET scanner and ex vivo gamma counting. This allows for the specific localisation of the two receptors within the brain and the visceral organ system.

 

Ms Nosihle Msomi

BSc (Hons) Human Physiology- Cellular Physiology

Estrogenic and androgenic activity in selected over-the-counter (OTC) antihistamines available in South Africa 

The endocrine system plays a major role in ensuring internal regulation of the body (homeostasis) through the use of hormones which are chemical signals channelled throughout the body to bind to receptors at target tissues and cells to illicit an appropriate response. It has been observed that there are a number of natural and man-made compounds, which include pharmaceuticals, which are able to either mimic or interfere with hormones produced by the body causing disruption of the endocrine system. These compounds are referred to as Endocrine Disruptive Chemicals (EDCs) and may lead to adverse effects during development, cancer, or even reproductive disorders. This project aims to determine if selected over-the-counter antihistamines, which are commonly used to treat allergy symptoms, may elicit EDC activity in estrogenic and androgenic bioassays, which may potentially result in adverse health effects in humans and the environment.

 

Ms Monique Vermaak

BSc (Hons) Human Physiology- Cellular Physiology

Identification of missense single nucleotide polymorphisms in the G protein-coupled oestrogen receptor that may affect its cell surface expression and signalling in a breast cancer model

The G protein-coupled oestrogen receptor has been shown to play a role in breast cancer metastasis. How the receptor is involved in this process is still unknown, however a single nucleotide polymorphism (SNP) in the N-terminal of the protein prevents receptor trafficking to the plasma membrane and causes trafficking to the nucleus where it supposedly behaves like a transcription factor. This variant is also believed to be involved in more aggressive cancer phenotypes. Therefore, the purpose of this study is to identify more SNP’s that may influence the function of GPER and to assess their effect on cell proliferation, migration and adhesion.

 

Ms Madison Tonkin

BSc (Hons) Human Physiology- Cellular Physiology

Identification and potential pharmacological chaperone rescue of oxytocin receptor mutations that cause decreased cell surface expression

The oxytocin receptor is a G-protein coupled receptor which has important roles in social behaviour, lactation and parturation. Mutations can cause the receptor to be non-functional, often due to misfolding of the receptor structure and intracellular retention/degradation by cellular quality control machinery. This project aims to determine the cell surface expression of selected oxytocin receptor mutants identified in human patients and to examine whether any retained mutants identified can have their cell surface expression restored using a putative pharmacological chaperone.
 

MSc projects

 

Ms Alexis Schwulst

MSc Human Physiology

Investigation into the potential biased signalling of the neurokinin 3 receptor

Neurokinin B (NKB) and its cognate GPCR, NK 3 R is an important regulator of the

hypothalamic-pituitary-gonadal (HPG) axis which controls sexual development and reproduction. Biased signalling is an established phenomenon in GPCR biology describing the mechanism by which different ligands or cellular contexts influence the recruitment of different intracellular signalling pathways. Biased signalling therefore has important ramifications in understanding the physiological and pathophysiological roles of GPCRs in human biology, but also for the drug development process. The aim of this project is to examine the differential recruitment of intracellular signal transduction pathways by NK 3 R and by doing so improve our understanding of the physiological responses and roles of this receptor.

 

 

Ms Sharika Hanyroup

MSc Human Physiology

Investigating the potential of small molecule FSH ligands as pharmacological chaperones.

Follicle-stimulating hormone (FSH) plays an important role in the endocrine control of reproduction in both male and females. Its functions are mediated through its cognate G protein-coupled receptor (GPCR), the FSHR. Mutations of FSHR may result in receptor misfolding and intracellular retention, with the result being reproductive dysfunction. Pharmacological chaperones have shown rescue of cell surface expression of misfolded GPCRs and have great therapeutic potential for the treatment of disorders attributed to protein misfolding. This project will characterize natural inactivating mutations of the FSHR occurring in patients with reproductive dysfunction and the ability of a range of FSHR interactive small molecules to rescue expression of misfolded, mutant FSHRs.

 

 

Ms Tarryn Radomsky

MSc Human Physiology

Identification and characterisation of small-molecule GHRHR-interactive compounds

Growth hormone-releasing hormone (GHRH) and its receptor (GHRHR), play an essential role in the regulation of growth hormone secretion from the anterior pituitary. In addition, GHRH also has several extra-pituitary effects, many of which are related to its mitogenic properties in many tissues. Indeed, GHRHR is known to be pro-proliferative in many cancers. Peptide antagonists and agonists are currently available as treatments for GHRHR disorders and are being developed as potential cancer therapeutics, however no non-peptide therapeutics currently exist. This project focuses on the identification of putative GHRHR interactive small-molecule compounds using in silico docking and subsequent in vitro functional validation. Some ‘hit’ compounds have already been identified in preliminary studies and these are now being further refined and characterised.

 

 

Mr Leslie Pedzisayi

MSc Human Physiology

Investigating the role of cell-to-cell communication in determining metastatic behaviour of breast cancer cells

No cell is an island. Cells are in constant communication with other cells and their immediate environment. This communication and what is communicated (biomolecules) dictate, shape or influence much of the cells functions. The exchange of biomolecules has been shown to alter the behaviour of the recipient cell. The high mortality rate associated with cancer is a result of metastatic spread. Therefore, the exchange of biomolecules affecting or improving metastatic spread is an important research question. Our study aims to investigate the role of intercellular communication in determining the metastatic behaviour of breast cancer cells. 

 

Ms Felicia Azubuike

MSc Human Physiology

Investigating the Role of the Kisspeptin Receptor, KISS1R, in the Regulation of Breast Cancer Cell Proliferation and Migration.

Kisspeptin and its receptor, KISS1R have been shown to suppress metastasis in most cancers such as prostate, ovarian, lung and oesophageal cancer. Kisspeptin/KISS1R signalling suppresses cancer metastasis in these cancers by suppressing migration and invasion. However, in breast cancer it has been shown to promote metastasis. High KSS1R expression has been shown to be associated with more aggressive or metastatic cancers. The exact mechanism through which KISS1R promotes breast cancer metastasis has not been fully elucidated. Therefore, the aim of my research is to decipher the role of KISS1R in breast cancer cell migration, invasion and proliferation. Through this study we will be able to determine the cellular cues that are responsible for the pro-metastatic effect of KISS1R in breast cancer.

PhD projects

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Dr Craig Grobbelaar

PhD Human Physiology

Gonadotropin releasing hormone-oetradiol conjugates as novel drugs for prostate cancer

KNDy (kisspeptin/neurokinin B/dynorphin) neurons of the hypothalamus are important for mediating the secretion of Gonadotropin-releasing hormone (GnRH), the master hormone regulator of the neuroendocrine reproductive (hypothalamic-pituitary gonadal; HPG) axis. This project entails investigating the effects of selective estrogen receptor modulators, neuroleptic-induced hyperprolactinaemia and acute stress on the KNDy network in rats. An understanding of the effects of these factors on stimulation and/or inhibition of kisspeptin, neurokinin B and dynorphin in relevant hypothalamic regions and the subsequent effects on the HPG axis will afford a great deal of significance for a wide range of issues affecting reproductive health and disease, as well as the treatment thereof. 

 

Ms Mandie Botes

PhD Human Physiology

The role of the G protein coupled oestrogen receptor in the regulation of metastatic parameters in an in vitro breast cancer model

The G-protein coupled estrogen receptor (GPER) has been shown to influence the metastasis of breast cancer.  However, much controversy exists regarding the localization of the receptor in the cell and the signalling pathways it activates.  Literature suggests that a single nucleotide polymorphism (SNP) in the N-terminal of the protein changes the glycosylation status of receptor and causes it to be trafficked from the plasmamembrane and endoplasmic reticulum to the nucleus where it behaves like an estrogen responsive transcription factor. The aim of study is to determine the prevalence of the two GPER variants in various breast cancer cell lines, the difference in signalling cascades activated by each variant and their possible roles in the metastasis of breast cancer.

 

Ms Ane Pieters

PhD Human Genetics

Identification and functional rescue of inactivating G protein-coupled receptor mutations in

European and South African hypogonadal patients

The hypothalamic-pituitary-gonadal (HPG) axis regulates reproduction. Studies of patients with congenital hypogonadotropic hypogonadism (cHH), characterised by pubertal failure and infertility have revealed many novel regulatory inputs to the HPG-axis. Many of these inputs are mediated by G protein-coupled receptors (GPCRs), but much remains to be elucidated and defined. We have identified GPCR variants in a cohort of European and South African patients with cHH. This study aims to establish whether these GPCRs are involved in the control of the reproductive axis and could contribute to cHH phenotype.

 

Post doctoral projects

 

Dr Abe Kasonga

Post-doctoral fellow

Gonadotropin-Releasing Hormone-Estrogen Conjugates and Bone

Androgen depletion through gonadotropin-releasing hormone (GnRH) analogues is a widely used method of treatment in prostate cancer therapy. However, the associated depletion of estrogens, which are derived from androgens, can result in bone loss. The study aims to investigate the in vitro effects of conjugates of GnRH analogues to estrogens in osteoclasts to determine whether these analogues could potentially prevent bone loss.

 

Dr Zulfiah Mohamed-Moosa

Post-doctoral fellow

Investigating the use of pharmacological chaperones for the rescue of mutant G protein-coupled receptors

Mutations in G protein-coupled receptors are implicated in many endocrine disorders. Inactivating mutations can impede interactions with ligands or down-stream signalling components, but often cause receptor misfolding and failure of translocation to the cell membrane thereby preventing function. Pharmacological chaperones, cell-permeant molecules which interact with and stabilise misfolded mutant receptors, have been identified for several GPCRs. This study investigates the ability of pharmacological chaperones to rescue mutant receptors and restore function. 

 

 

Previous projects
 

Mr Lorenzo Fernandes
MSc Human Physiology

Restoring the function of inactivating mutations of G protein-coupled receptors

Many G protein-coupled receptors (GPCRs), are known to be, or have the potential to be, involved in the neuroendocrine control of reproduction. Mutations in GPCRs often cause them to be intracellularly retained and cause disease. Restoration of membrane trafficking of intracellularly retained GPCRs has been shown to be achievable through the use of pharmacological chaperones (PCs). PCs are cell-permeant molecules which interact with misfolded proteins, promoting their correct folding and enhancing their trafficking to the cell membrane, thus “rescuing” their function. Although PCs provide an attractive, novel therapeutic option, one limitation is that the PCs must be cell-permeant and therefore able to enter the cell, in order to interact with the newly synthesised protein as it is folded in the endoplasmic reticulum. Unfortunately, the majority of endogenous GPCR ligands are not cell-permeant. Therefore, different methods to convey cell permeability to these ligands as an alternative means of “rescuing” intracellularly retained mutant neuroendocrine GPCRs is being examined.
 

Ms Robin du Preez
MSc Human Physiology

Characterisation of potential novel small molecule therapeutics targeting the growth hormone releasing hormone receptor 

Growth hormone releasing hormone (GHRH) elicits its effects through binding to the growth hormone releasing hormone receptor (GHRHR). GHRH regulates the secretion of growth hormone (GH) from the anterior pituitary. Disorders such as gigantism, acromegaly and dwarfism can occur when there is an over or under secretion of GH. GHRH is considered to be a primary regulator of the pituitary GH axis, but also has various other important extrapituitary effects (eg. in cancer and aging). Thus, GHRH and GHRHR are very important therapeutic targets, and peptide agonists and antagonists have been developed. However, no orally-active non-peptide therapeutics currently exist. GHRHR belongs to the G protein-coupled receptor (GPCR) family. Remarkable progress has been made in the field of GPCR structural biology over the last few years, opening up possibilities for applying in silico structure-based approaches to GPCR drug discovery efforts, including in silico docking, a computational method of docking small flexible molecules to a protein structure. Using in silico docking, several GHRHR interactive compounds have been identified. In this study, the in vitro activity of these compounds will be examined. The ‘hit’ compounds will be further refined through “in catalogue” screening, aiding in the process of producing new effective therapeutic compounds.  
 

Ms Genevieve Auger
MSc in Medical Immunology

Identification of novel hypothalamic G protein-coupled receptors involved in the control of reproduction

Many G protein-coupled receptors (GPCRs) are expressed in the hypothalamus and are known to be, or have the potential to be involved in the secretion of gonadotropin-releasing hormone (GnRH). GnRH is the master regulator of the hypothalamus-pituitary-gonadal axis which controls reproduction and fertility. This project aims to examine three mutant hormone receptors; Oxytocin receptor, Neuropeptide receptor Y4 and Leucine rich repeating 5 GPCR, identified in human patients suffering from hypogonadotropic hypogonadism (HH). HH patients are characterized by incomplete or partial pubertal development due to GnRH deficiency. These mutant GPCRs will be examined in vitro in order to determine if they cause non-functionality and could therefore be causative to the phenotype of HH patients. Characterization of novel GPCR mutations implicated in HH will provide insight into the physiological and pathophysiological roles of these receptors in the neuroendocrine control of reproduction. 

Ms Humbulani Ravhura
BSc Hons Biochemistry UNISA, Research Assistant CNE

Temperature rescue of a selection of luteinizing hormone receptor mutants

Luteinizing hormone receptors (LHRs) are cell surface G-protein coupled receptors that play an essential role in reproductive physiology. Genetic mutations in these receptors cause them to be trapped in the cell and subjected for degradation and this leads to a range of reproductive disorders. We have demonstrated that, using the LHR as model, some of these mutant receptors can be rescued and functionally expressed on the cell surface by treatment with the pharmacological chaperone, LHR-CHAP.  The aim of this project is to determine if rescue by reduced temperatures (which should aid protein folding) can be used as an index for a mutant receptors ability to be rescued by a pharmacological chaperone. Because not all mutated receptors are targets for pharmacological therapy, it will be useful to identify those to focus on for drug development.

Ms Alexis Schwulst 
BSc (Hons) Human Physiology - Neurophysiology

Identification of novel potential pharmacoperones to rescue Neurokinin B receptor mutations

Neurokinin B (NKB) is an important regulator of the hypothalamic-pituitary-gonadal (HPG) axis which controls sexual development and reproduction.  The role of NKB in the reproductive axis became clear when mutations in both the NKB ligand and its cognate G protein-coupled receptor (GPCR) NKBR, were shown to be implicated in reproductive disorders including hypogonadotropic hypogonadism. Many GPCR mutations cause receptor misfolding and subsequent intracellular retention/ loss of surface expression. The aim of this project is to identify pharmacological chaperones (PCs) able to rescue intracellularly retained mutants of the NKBR. A range of non-peptide NKBR selective ligands are being examined for PC activity looking at effects of treatment on mutant receptor expression profiles.

Ms Abigail Lightbody
BSc (Hons) Human Physiology – Neurophysiology 

Identifying potential novel pharmacoperones for the rescue of cell surface expression of follicle-stimulating hormone receptor mutants.

Follicle-stimulating hormone is an important hormone in the endocrine control of reproduction and has several functions in both male and female gamete maturation as well as in the development of secondary sex characteristics. The follicle-stimulating hormone exerts its effects through its cognate receptor (FSHR). Mutations which cause the misfolding of this G protein-coupled receptor protein disrupt its cell surface expression, resulting in several reproductive conditions such as hypergonadotropic hypogonadism, primary or secondary amenorrhea, variable development of secondary sex characteristics and infertility due to the arrest of follicular development. Pharmacological chaperones which can rescue cell surface expression of misfolded proteins have great therapeutic potential for treating many diseases/disorders attributed to protein misfolding, including reproductive disorders caused by follicle-stimulating hormone receptor mutations. Therefore, we are testing FSHR-selective non-peptide ligands for pharmacological chaperone activity.

Ms Mandie Botes
MSc Human Physiology

Identification of the target of EE-15-one and elucidation of the pathway leading from EE-15-one exposure to anoikis

This project focuses on identifying the target and the signalling pathway of an estrone derivative with cytotoxic effects on breast cancer cells in vitro. The same effects are seen in estrogen receptor positive cell lines as well as triple negative breast cancer.  Why is this important?  According to the latest statistics, women have a 1 in 8 chance of developing breast cancer at some point in their life.  It is the leading cause of female related cancer, with triple negative sub-types being more aggressive and more resistant to treatment.  However, we have made little advances in developing chemotherapeutics that will be effective against triple negative breast cancers and prevent the cancer from metastasizing to secondary sites. This project will aid in identifying a possible target for treatment.

Ms Carmen Riekert
MSc Human Physiology

Investigating the mechanisms behind pharmacological rescue of mutant G protein-coupled receptors

Mutations of G protein-coupled receptors (GPCRs) commonly cause impaired receptor expression as a result of defective receptor folding, maturation or premature degradation. This defective expression results in impaired signalling and thus a vast variety of diseases are attributed to mutated GPCRs. As soon as the normal conformation of a GPCR is compromised the receptor can be retained as a proactive mechanism to eliminate possible physiological dysfunction. However, not all compromised conformations are deleterious. This forms the basis of possible GPCR rescue induced by pharmacological chaperones. Pharmacological chaperones are small, often hydrophobic, ligands which interact with and enable mutant GPCRs to escape the strict endoplasmic reticulum quality control (ER QC), allowing the misfolded but not dysfunctional receptor to escape and be trafficked to cell surface. However, the mechanisms behind the “rescue” remain unclear and we therefore aim to use luteinizing hormone receptor mutants as model to explore these processes in more detail.

Ms Tamarin Jurgens
PhD

Investigation into the effects of a novel estradiol analogue on hypoxic breast cancer tumour cells

This project aims to investigate whether triple negative breast cancers, such as the BT-20 cell line, grown in 3D (which mimics in vivo small breast tumour architecture) could be used as a reliable platform for drug discovery and testing. Using this system this project investigates the ability of novel antimitotic 2-methoxyestradiol (2ME) derivatives to overcome hypoxia-induced chemoresistance in breast cancer cells. The derivatives were designed as carbonic anhydrase (CA) inhibitors and as CAIX is unregulated in hypoxic cells these derivatives could potentially help us to understand the mechanisms and underlying cellular pathways involved in the induction of chemoresistance. 

Ms Stacey-Lee Leijenaar
PhD

Functional Characterisation of Gonadotropin-Releasing Hormone-Estrogen Conjugates

In many countries, prostate cancer is one of the most common causes of cancer related deaths. It is an androgen-dependent disease and, as androgen secretion is regulated by the hypothamic-pituitary gonadal axis, the master regulator of which is gonadotropin-releasing hormone (GnRH), GnRH analogues are the mainstay of prostate cancer treatment through androgen depletion. However, the concomitant depletion of estrogens, which are synthesized from androgens, produces adverse side-effects of hot flashes and loss of bone and libido. We proposed that GnRH analogues conjugated to estrogens could retain both GnRH and estrogen activities in a single molecule, thereby achieving both androgen deprivation and estrogen replacement with resultant amelioration of side-effects. The aim of this study was to examine the in vitro functional activity of conjugates of GnRH analogues to estradiol or the phytoestrogen, genistein, at GnRH and estrogen receptors in order to determine their potential as novel prostate cancer therapeutics.