Phosphofructokinase 1

So, what you have to keep in mind is that AMP kinase signaling goes through various control, because it's a kinase, specific enzymes.

So, for example, the AMP kinase affecting PFK1, PFK2.

the autophagy going through the ULK1, apoptosis going through P53, the proteins involved in peroxisome proliferator activator receptor, which involves mitochondrial biogenesis.

All those systems are going to be turned on.

That was what some of the first components of the last lecture 18, the first 10 or 12 lectures in this series, what I would call dynamic reprogramming via post-translational modifications, allosteric interactions.

Remember the PFK1 story, and then the trafficking of metabolites, which is far more complex than that.

And then finally, lipid metabolism and the endomembrana system, which involves thousands and thousands of interacting platform opening and closing derivatization.

in a time interval that's less than one minute that controls the immediacy of how cells respond to such thing as a tumor microenvironment and then the longevity of that response because the endomembranous system doesn't just dissolve.

Go back and think about the regulation of phosphofructokinase 1 by Asel Coe.

because acyl-CoAs will build up in type 2 diabetes.

Therefore, looking at the regulation of phosphofructokinase in patients that also have a comorbidity such as simply obesity, because there'll be a lot more acyl-CoA, generating more of a production of ectopic adiposity, which will lead to higher levels of pro-inflammation, that PFK1 movement because of its interaction with acyl-CoA will contribute to that dysfunction.

Anyway, glucose transport proteins like GLUT1 and GLUT4, they always facilitate glucose transport into actual card-carrying insulin-requiring cells.

So insulin is required for those two glucose transporters to make it to the plasma membrane.

And of course, that work was done with chromatography, mass spec, mass spec.

Now, the acylation of PFK1 is reversible, and you know this.

because we talked about the protein deacylases.

Remember those, those APTs? So that's a natural phenomenon in the cell.

So you're not likely to have high levels of a continuum of a population of PFK1 that's going to be hyperpalmitoylated, right? We only know that that occurs.

And we know it's a thioester because the early work, if you treat a thioester with a reagent known as hydroxylamine, then you lose that fatty acid bound.

You know that is a thioester linkage.

So your professor here did that kind of research back in the day when I was doing research.

For example, rate-limiting enzymes and pathways.

Phosphofructokinase 1, for example, something like that.

All right.

Now, you couple that with your standard single-cell metabolic profiling, and what you observe in some immune cell populations is more detailed than what had been described recently.

But let me finish it.

You see, the inhibition of phosphofructokinase 1 remember bipadiacyl-CoA, remember those cysteine residues making thioesters of that palmitate at four different positions on the enzyme PFK1, and how that then resulted in a reversal of inhibition by cellular thioesterases, and that ultimately that represented an unrecognized, until then, mechanism of through which glycolysis and mitochondrial beta-oxidation of fatty acids are tightly coordinated.

So, I want you to think deeper about this.

The major cytosolic myocardial lyophospholipase that was purified from myocardium was shown to be a lyophospholipase and an acyl-CoA hydrolase.

That enzyme will do all three of those activities, though.

And what's that enzyme called? APT1.

Now, APT1 in this model system in the mouse catalyzed the removal of palmitic acid, which was esterified, not just the PFK1, but to G-protein cysteine residues.

So also thioesters, you see.

Now, the hypothesis they generated was was that increased beta-oxidation of fatty acids results in elevated intramitochondrial acetyl-CoA concentration and an increase in citrate, which is transported to the cytosol by, of course, the citrate carrier.

Consequently, cytoplasmic citrate levels increase, which leads to the direct inhibition of phosphofructokinase 1, at the citrate regulatory site, an allosteric site.

And hence the accumulation of glucose 6-phosphate results.

So that elevation in the concentration of glucose 6-phosphate would then decrease hexokinase activity and thus decrease net glucose uptake.

immune network, killing, for example, tumors or, in fact, in other systems, parasite or intracellular bacterial or any kind of infectious status, right? Because we're talking about tumors here because that's the topic of this lecture series.

But you understand this is happening in any kind of immune synapse.

Now, I hadn't forgotten, and I hope you haven't either, two lectures ago, I was talking all about phosphofructokinase 1 allosteric regulation.

Remember that? Please recall that.

Now that will alter the phosphorylation state of a complete series of metabolic enzymes in nested so-called pathways.

How so? For example, PFK1, that's phosphoprotein kinase 1, rate-limiting enzyme in glycolysis.

As you know, or maybe you don't, it's allosterically activated by fructose 2,6-bisphosphate, which is synthesized by a bifunctional phosphofructokinase 2, FBPase 2.

Now, when that protein, the bifunctional PFK2, FBPase 2, FBPase stands for fructose bisphosphatase 2, And that complex generates fructose 2,6-bisphosphate, which is the allosteric regulator of phosphatidyl kinase 1, the glycolytic enzyme.

So this can also be very athletic people.

glycolysis must be stimulated as AMP levels rise.

So this is recognized by that highly complex ordered system because I can tell you that AMP also controls PFK1 directly, just adenosine monophosphate.

but in this skeletal muscle contraction.