The transfer of complex mixtures of signals and nutrients between individuals is a key step in several biologically important events in our lives, such as breastfeeding and sexual intercourse. However, we know relatively little about the ways in which the molecular gifts involved are packaged to ensure their successful delivery to the recipient.
By studying such events during mating in the fruit fly, researchers at the University of Oxford have identified a new communication mechanism in which nutrients and signals are combined in fatty droplets that stably store their bioactive cargos in males, until they are transferred to females when they dissipate within minutes. These specialised multi-molecular assemblies called microcarriers, are made by the prostate-like accessory gland of the male and contain a central fatty (lipid) core wrapped with multiple proteins, including a molecule called Sex Peptide. When Sex Peptide is released in the mated female, it stimulates her to produce more progeny and reprogrammes her brain so she rejects other male suitors.
Although Sex Peptide is only produced by a limited group of fruit fly species, lipids and lipid droplets are secreted by many glands, including the human prostate and breast. Preliminary work in flies suggests that one of the genes that is essential for the release of microcarriers from secreting cells also plays a critical role in human glands, including the breast. In fact, this regulatory gene is highly expressed in some breast cancers. This suggests that the mechanisms controlling microcarrier formation may be evolutionarily conserved and that microcarriers may play much broader roles in physiological and pathological cell-cell communication, which have yet to be recognised.
This new cell communication mechanism could have implications for breast cancer and understanding its pathology because the regulatory gene essential for driving reproductive success is also expressed in some breast cancers, so if we can better understand the gene's mechanism, it might be possible to understand how breast cancer can become pathological.
The study was a collaboration between the groups of Professor Clive Wilson and Associate Professor Deborah Goberdhan from the Department of Physiology, Anatomy and Genetics, at The University of Oxford. This work has been supported by funding from the Biotechnology and Biological Sciences Research Council (BBSRC), Cancer Research UK, the Wellcome Trust and the Medical Research Council
Paper to be published in PNAS:
Drosophila Sex Peptide Controls the Assembly of Lipid Microcarriers in Seminal Fluid