cAMP & PKA - Video Tutorials & Practice Problems

cAMP & PKA

So here we're going to briefly revisit our map of the lesson on bio signaling pathways, which is down below right here. And of course, we've been exploring this map by exploring the left most branches first. And so we've already introduced G protein coupled receptors or GPC ours. And we've talked specifically about the stimulatory, a dental it cyclist GPC, our signal transaction pathway. And so here in this video we're going to continue to talk more and more about this pathway by talking about the secondary messenger C amp and the enzyme protein kinase A or P k A. And so let's go on and get started talking about these. So now that we've covered stimulatory, a dental it cyclist GPC are signaling here, we're going to continue to talk about that same pathway by focusing on the secondary messenger C amp and the enzyme protein kinase A or PK for short. And so in this video. Specifically, we're going to focus on the production and the function of the secondary messengers C. Amp. And so recall from our previous lesson videos that the effect er enzyme a dental it cycles actually converts its substrate p into the secondary Messenger C AMP, which is really just an abbreviation for cyclic adenosine triphosphate. So you can see C amp comes from that name. And so if we take a look at our image down below, over here on the left hand side, notice on the left, we're showing you the structure of a T. P, which we know again is the substrate for the effect er, enzyme a dental, it cyclists. And so notice here as the catalyst to this particular reaction that we're showing. We have the enzyme a dental, it cyclists in its active form. And so when a dental it cyclist is activated, it can actually convert its substrate 80 p into the secondary messenger that we see over here. See amp. And so you can compare the structure of C. Amp with a TP to get a good idea that they are related to one another. So notice that two of inorganic phosphates here are released and, uh, in the process uh, the phosphate here is cyclic, which is why it's called cyclic Adina seen mono phosphate because it only has one phosphate group that is in a cyclic form that, as we see down below. Now, really, this secondary messenger molecule that we see here see AMP again, is a secondary messenger that goes on to activate the enzyme that's called C amp dependent protein kinase a or just PK A. For short. And so you can see PK comes from this abbreviation for protein kinase A, and this is a C AMP. Dependent enzyme. And so Pekka is only going to become active in the presence of the C. AMP. Secondary Messenger. And so therefore, what we can say here is that C. Amp. Is going to function as an Alice Terek activator, which recall that we can symbolize using a positive sign for activation. And so CF is an Alistair activator for the enzyme protein kindness? A. And so if we take a look at our right side of the image over here, notice that we're showing you the activation of the enzyme PK and notice that we're showing you specifically. Four C AMP molecules and these four cm molecules will bind to the inactive form of PK. And so when C amp binds to the inactive form of P K A. As we see up above the sea and molecules are these little purple guys that we see when they bind to the inactive form of the PKK. It actually activates the these other two subunits of Pekka and we're going to talk more detailed specifically about this process right here and the activation of Pekka in our next lesson video. But for now, what you can see is that C amp is acting as an Alice Terek activator for P K A. To activate it. And so this year concludes our introduction to the production and function of CM, and I'll see you guys in our next video.

cAMP & PKA

and this video, we're going to talk about the activation of CME dependent Protein kinase A or P K A. For short. Now recall from our previous lesson videos. That kindness is are enzymes that utilize energy in the form of a teepee in order to fuss for late there substrates or at a phosphate group to their substrates and, of course, protein kindness. A is, indeed a kindness itself, so it is going to phosphor late. It's substrates using ATP now. It's also important to note is that in the absence of any secondary messenger, see AMP. The enzyme protein, kinase A or P K is in its inactive hetero te trimmer form. And so hetero, we know is a prefix that means different. Tetra is a prefix that means four, and so that means that it's going to have four sub units that are different from each other. They're not all identical, and so, and it turns out that it actually has to regulatory sub units and two catalytic subunits. So it's referred to as our to see to where the are represents the regulatory sub units and there are two of them, and the C represents the catalytic subunits and again there are two of them. And so if we take a look at our image down below, notice up here at the top left, we have a little reminder of our identity. It cyclist GPC are signaling pathway. So we have our hormone signaling like an epinephrine or adrenaline will bind to the GPC arm or specifically, the beta Adrianne ergic GPC are causing a confirmation. I'll shift in this. GPC are that ultimately activates the G protein that we have down below where it's going to promote it. To exchange it's low energy g d. P for a high energy GTP. And so that is going to promote the dissociation of the Alfa sub unit, which goes on to activate the effect er enzyme a dental it cycles, which we mentioned in our last lesson. Video converts the substrate a teepee into the secondary messenger. Uh, see amp Now what you'll notice is here we're showing you the structure of the protein kindness. A. Before Cmte has a NIF effect on its structure. And so we said that PK exists as an inactive hetero te trimmer with four sub units that are not identical. Uh, more specifically to regulatory sub units, which we abbreviate with ours, and to catalytic subunits, which we abbreviate with sees. And so when Piquet is in this hetero tetra reform it's in, it's in active form, so it will not be performing its function. Now. It's important to note is that C. Amp it is going to act as an al hysteric activator to protein, Kinda said, and more specifically for C amp molecules are needed to bind to the regulatory PK sub units. And that is going to release the two, uh, the two catalytic lee active PK sub units. And so these catalytic Lee active PK sub units, of course, are going to be able to fuss. For late. They're substrates. More specifically, the PK is a Syrian three inning kindness, so it will be able to fast for late Syrian three inning residues on their target proteins in order to alter the activity of their target proteins. And ultimately, the altered activity of the target proteins leads to the cell response. And so if we take a look at our image down below, notice that it specifically takes four cyclic A M P molecules in order to interact with the inactive p k A. To generate the active form of PK over here. And so notice that we have these four C amp molecules here that bind to the regulatory sub units of PK and that causes the dissociation of the regulatory sub units and releases the two catalytic lee active sub units that we can abbreviate with seized down here. And these two catalytic lee active PK sub units can then, uh, act as Syrian three and mean kindness is too fast for late there substrates. And so what that means is they could take an inactive enzyme and phosphor elated to create an active enzyme that would lead to the cell response or again. Since phosphor relation does not necessarily always mean activation, it could take an active enzyme that is not phosphor, elated and phosphor related to create an inactive enzyme, and that would also lead to the cell response. But ultimately, the main take away here is that it takes four C AMP. Molecules to activate the two catalytic peek a sub units. And so, really, this here is, uh, the conclusion toe how see amp dependent protein kinase a or P K is activated and we'll be able to get some practice applying these concepts as we move forward in our courts, so I'll see you guys in our next video.

cAMP & PKA Example 1

all right. So here we have an example problem that wants us to order each of the steps in the activation of Peak A by numbering them one through four and notice the first step is already numbered for you, starting immediately after a dental it cyclists activation. And so notice that immediately after a dental it cyclist activation were told that the very first step here is that site of Solich Cmte. Concentration increases. And so what we need to do is number each of these other three steps that we see down below in the proper order, using numbers 23 and four. And so, of course, immediately after a dental it cyclist activation after cited Solich cm concentration increases. The next thing that's going to happen is that C. Amp is going to be able to act as an Alice Terek activator. To peek a and so to see aunt molecules will bind to each of the peak a regulatory sub units where we know that there are two regulatory sub units. So really, there are four total cmte molecules needed toe regulate the peak a sub units, and so this event here will be the second event to take place. And then after these, uh, see aunt molecules bind to the regulatory sub units. The next event is that the regulatory sub units of the PKK need to disassociate from the catalytic sub units so that the catalytic subunits can be released in their active forms. And so what we're saying here is that see, here is going to be the third event that occurs immediately after this. And then, of course, last but not least, what we have is the last step. Step four is right here, which is that the free catalytic subunits that were released can then Foss for late proteins on their serene and three any residues. And so we could go ahead and label this as Step four. And so, really, this is the answer to this practice problem, and I'll see you guys in our next video

Which of the following statements about protein kinase A (PKA) is false?

• A. PKA binds a total of four molecules of cAMP, two molecules on each of the regulatory (R) subunits.
• B. PKA binds a total of four molecules of cAMP, one on each of the four subunits.
• C. Once active, the catalytic (C) subunits dissociate and phosphorylate target proteins.
• D. When inactive, PKA is a tetramer of two regulatory (R) and two catalytic (C) subunits.

cAMP & PKA

So now that we've talked about the production of C AMP and the activation of Peak A in this video, we're going to introduce the inactivation of the secondary messenger molecule C amp and the inactivation of the enzyme peek A And so recall from our previous lesson videos that the G t p Ace activity of the G protein Alfa sub unit is ultimately what is going to inactivate or terminate The GPC are signaling pathway to help reset that entire pathway. But what we did not get to mention in our previous lesson videos is that there are also two other events that also allow for the termination of the GPC are signaling pathway. And those two events are going to be the inactivation of C amp and the inactivation of PK. And so we've separated out these two events into event number one and event number two down below and noticed that these events are also, uh, correspond with the events that you see down below, labeled one and two. And so again, the first event here is going to be the inactivation of C AMP and so see amps. Signaling effect can actually be turned off by decreasing the concentration of C AMP within the cell and the cell can decrease its concentration of C AMP using the enzyme known as C AMP phosphate O dia stories and so see AMP. Foss phone. Oh di s a raise is an enzyme that is going to convert the secondary messenger molecule C amp into its non cyclic version a. M p. And so notice that the really difference between, uh, the real difference between C. AMP and A MP is the sea here that is not present in a MP and so recall that the C represents cyclic and really, that's all that's changing with a MP, and we'll be able to see that down below in our image. But the biggest thing to note is that this a MP actually does not activate PK A. Like what? See amp does. And so it's actually a big deal to convert CM into a MP. And of course, this by converting CM into a MP that's going to decrease CM concentration and helped turn off the signal and essentially help terminate the GPC are signaling pathway. And so if we take a look at our image down below notice again. Up here at the top left, we have a little reminder of our stimulatory. GPC are signaling pathway, so we know that the hormone extra cellular, like an epinephrine or adrenaline, will bind to the beta agin ergic. GPC are causing a confirmation all shift that promotes GTP replacement of G, d. P. And that is going to allow the dissociation of the G protein Alfa sub unit to diffuse and activate the A dental it cyclists, defector enzyme and that will convert its substrate. A teepee into see AMP. And then, of course, of a c amp here is going to promote, uh, the cell response like we talked about in our previous lesson video. But if we want to turn off this effect, if we want to turn off the signaling pathway and reset the pathway, then we need to get rid of some of the CME and decrease the concentration within the cell to turn off the pathway. And so that's exactly where CM Foster Diocese race comes into play because it converts the see Aunt molecule over here, the cyclic version of the phosphate group here into a M P, which we have over here. And and most important, part about a MP is that it's phosphate group is not going to be in the cyclic version. And so it's going to look like this so we could go ahead and label that as the phosphate group and so notice that it is not cyclic over here, whereas over here it is cyclic. And so a MP is not able to regulate PK A. Like what See amp. Is usually able to do and so see and foster Diocese Race is able to again help turn off the entire signaling pathway now moving on to step number two, which is again going to be the inactivation of Peak A. On the other hand, uh, notice that PKS activity is going to be reversed by searing 3 phosphate ASIS. And so phosphate taste is, you might recall from our previous lesson. Videos are pretty much enzymes that are the opposite of kindnesses, and so Syrian three named phosphate cases are going to remove phosphate groups from their substrates instead of add phosphate groups to their substrates like what? Kindnesses dio. So if we take a look at our image down below what you can see is that normally see amp would bind to the regulatory sub units of PKK, which is again this is the inactive form of PK over here. And when the CME binds to the regulatory sub units, it would release the catalytic Lee active, uh, PK sub units here, which we can label these as active and then these catalytic lee active PK sub units, because their kindness is they can fuss for late enzyme substrates and that will lead to the cell response. But of course, even with the activity of CME Foster Diaries and even by, uh, cleaving the GTP in the G protein, uh, that is not going to remove the phosphate groups that are on these enzymes. And so if we really want to reset the pathway and turn off the signaling pathway, then we need a way to remove the phosphate groups. And that's exactly where the Syrian three and in phosphate taste is come into play. And so over here and step number two, what you could see is that the foster taste is will remove the phosphate groups that the PK added to its targets. And so that is going to help revert back the entire process and help to reset the entire pathway, essentially helping to inactivate Peek a further and so really, this here concludes our introduction to the inactivation of C. AMP and PK, and we'll be able to get some practice with these concepts as we move forward in our course, so I'll see you guys in our next video.

What could be the result of a mutation in the R subunits of cAMP-dependent protein kinase A (PKA) that inhibits formation of the R₂C₂ protein complex?

• A. PKA will always remain in the inactive state.
• B. cAMP would drastically decrease PKA activity.
• C. PKA will always remain in the active state.
• D. No effective change occurs.

The image below is a schematic representation of PKA activation from epinephrine binding. Based on the provided numbers in the diagram, how many subunits of catalytically active PKA will there be?

• A. 1,000 molecules.
• B. 200 molecules.
• C. 100 molecules.
• D. 50 molecules.
• E. 400 molecules.