Do Major Facilitator Superfamily Domain Containing Proteins Respond to Glucose Starvation?

Sammanfattning: The human brain weighs around 2% of the total body mass, nevertheless it consumes about 20% of the total glucose intake. Glucose, the main energy source of the brain, is important for many processes, for instance as energy for synthesis of neurotransmitters. Therefore a stable glucose concentration in the brain is crucial. Unlike other macronutrients, glucose is able to cross the BBB through facilitated transport by glucose transporters (GLUTs) that belong to the solute carrier (SLC) superfamily. There are currently 65 SLC families with over 400 members in total. Out of 65 families, many belong to the protein family (Pfam) class major facilitator superfamily (MFS). There were 28 putative SLC transporters, 18 of them were called major facilitator domain containing proteins (MFSDs). Recently MFSD2A, MFSD2B, MFSD4A, MFSD4B and MFSD5 were grouped into SLC families making the total amount of current putative SLCs 23 In this project the effects of glucose starvation on MFSD6, MFSD6L, MFSD8, MFSD9 and MFSD10 in primary mouse cortex cultures were studied on protein and gene level through immunocytochemistry (ICC) and quantitative polymerase chain reaction (qPCR). All proteins except for MFSD10 were detected in the ICC. All except MFSD8 displayed a change in fluorescent intensity. MFSD6, MFSD6L and MFSD9 were upregulated after 3 h of glucose starvation compared with control. Gene expression was detected for all targets except for Mfsd6l. Gene expression alterations were found for Mfsd8, Mfsd9 and Mfsd10. The 3 h glucose starvation resulted in an acute response in the gene expression for Mfsd9 and Mfsd10 but was back to control levels after 12 h, while Mfsd8 respond after 12 h of glucose starvation. All of them were back at similar levels as controls when re-fed with glucose. In conclusion, all five MFSDs responded to glucose starvation at some point. For instance MFSD6 responds to glucose starvation on a protein level, Mfsd6 was however also the only gene out of the four tested that did not respond to glucose starvation on a gene level.