Exploration of the hemocyte surfaceome of Apis mellifera by a proteomic and transcriptomic approach

This study maps the surfaceome of Apis mellifera hemocytes, the protagonist cells in honey bee cellular immunity. The surfaceome, proteins expressed at the cell surface, is crucial as it determines how cells interact with their microenvironment. Through a combination of proteomic and transcriptomic analyses, 1142 genes encoding cell surface proteins were identified, revealing a high level of diversity. Our analyses identified receptors associated with the major insect immune pathways and proteins previously recognized as hemocyte markers in other invertebrates. Notably, several of the detected genes suggest to encode viral receptors, phagocytosis-related proteins, or proteins involved in hemocyte proliferation. A gene ontology analysis highlighted important functions of the hemocytes. The most prominent cluster was transmembrane receptor protein kinase activity, encompassing over 25 % of the identified terms. Other significant clusters included cell adhesion molecule binding, signalling receptor binding, olfactory receptor activity, and metalloendopeptidase activity. This study suggests several potential honey bee hemocyte markers and establishes a foundation for a novel hemocyte classification based on cell surface markers.