Understanding the roles of CD33 variants on microglial activation
Lead Research Organisation:
University of Cambridge
Department Name: Biochemistry
Abstract
Two microglial proteins play antagonistic roles in regulating phagocytosis. The first, TREM2 is a debris-sensor and the second, CD33, provides a brake on phagocytosis that is applied in the presence of sialic acid residues on surrounding glycoproteins. Common genetic variation in CD33 results in the loss of the sialic acid binding domain and/or a reduction in protein expression; both mechanisms favour de-repression of microglial phagocytosis, favouring the clearing of debris. The goals of this proposal are to determine the effects of these CD33 variants on i) microglial phagocytosis of debris and neurons; ii) microglial inflammatory signalling; and iii) the interaction with TREM2. We will use CRISPR to generate microglia or similar cells with each/both of the pro-phagocytic CD33 polymorphisms and shRNA or siRNA knockdown of TREM2. With these tools to hand, we will measure: phagocytosis of debris and neurons, signalling following inflammatory stimuli, and cytokine release. Subsequently, we may perform equivalent CRISPR editing in iPS lines in order to determine how these CD33 variants affect microglial function. This project addresses the BBSRC Strategic Theme: Bioscience for Health, by revealing the biological mechanisms underlying normal brain physiology, in order to sustain wellbeing throughout life.
People |
ORCID iD |
| Guy Brown (Primary Supervisor) |
Studentship Projects
| Project Reference | Relationship | Related To | Start | End | Student Name |
|---|---|---|---|---|---|
| BB/R506047/1 | 01/01/2018 | 31/12/2021 | |||
| 2007303 | Studentship | BB/R506047/1 | 05/01/2018 | 04/04/2022 |
| Description | We have found that CD33 is in fact very crucial to microglia activation by knocking down CD33 in mouse microglia cell lines and mouse primary cultures. We have also created variant specific lines to address one of the key questions of this project. We have found that there is a gain of function to the "protective" variant by enhancing the microglia activation paradigm without deleterious effects on healthy neurones/neuron-like cells in culture. We have created both mouse (BV2) over expression lines and also human (CHME3) over expression lines and we see very similar effects in both. Recently, we have found in the human cell lines that there is no effect of the variants on inflammation (i.e. cytokine release). Using the mouse over expressing line we were able to find that CD33M over expression directly effects TREM2 activation (i.e. phosphorylation of SYK). And desialylation of microglia appears to effect TREM2 signalling also. |
| Exploitation Route | Using the finding that the protective function may be beneficial, we or others could use different techniques/molecules to induce a larger proportion of this form and see if this is protective in relation to more disease specific models such as IPSCs and/or primary mixed cultures and inevitably whether CD33 and enhancing this protective variant is a good avenue for therapeutic intervention |
| Sectors | Healthcare,Pharmaceuticals and Medical Biotechnology |