There is a large store of several of the GLUT proteins internalised in many cell types. These can be activated by various stimuli to associate with the plamsa membrane and begin importing/exporting glucose. I am curious to know whether they actually bind glucose in this state and thus may form a local store of glucose the cell could utilise without having to break it down from more complex compounds.
I can find no references to support this, any help would be appreciated.
I guess you should ask the question in a different manner, glucose flows into the cells and signals from inside.
So does it bind directly the glut inside and activates their translocation or is it like for other glucose responding molecule that glucose-6P or other modified molecules which are responsible?
My understanding is the glucose is metabolized in cells, not stored as such.
In cancer there is a lot more glucose than normal. My question is whether there is storage in these cells. The GLUTs are often either retained on the plasma membrane or are induced to translocate based on the action of insulin or IGF. A couple of the GLUTs, (6,8 and 12) show very high intracellular levels and very low membrane associated levels.
Are they capable of binding (not just transporting) to glucose already inside the cell?
Immediately after uptake, glucose is converted to G6P by hexokinases. Intracellular Gluts, if they bind glucose, would thus be in competition with hexokinases. Under high glucose, excess G6P can bind to transcription factors (Mondo) that regulate the expression of TXNIP which in turn leads to Glut degradation. Inhibition of HKs (http://www.nature.com/srep/2013/130625/srep02070/full/srep02070.html) leads to reduced glucose uptake (https://www.landesbioscience.com/journals/cc/article/26461/). This would indicate that there is a direct correlation between HK activity and glucose uptake and perhaps no role for intracellular Gluts. But nature is complex ....
Even if the GLUTs did have a glucose molecule bound, I imagine there would likely only be one available molecule per protein, which would amount to an insignificantly small quantity of glucose stored.
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