Okay. So here we're going to revisit our map of the lesson on biosignalling pathways, which is down below right here. And, of course, we know that we've been exploring this map by following the leftmost branches first. And so we've covered G protein-coupled receptors or GPCRs, and we've talked all about the adenylate cyclase GPCR signaling system, including the stimulatory pathway that involves cAMP and PKA, and the inhibitory pathway that involves also drugs and toxins. And so now what we're going to do in this video is talk about another G protein-coupled receptor pathway, another GPCR pathway called the Phosphoinositide GPCR Signaling Pathway. And so let's get started talking about that.
So here we're going to introduce another classic example of a GPCR signal transduction pathway, which is phosphoinositide GPCR signaling. Now, depending on your textbook, sometimes they'll refer to this pathway as the phosphoinositide signaling pathway, but in other textbooks, they'll refer to it as the inositol phospholipid signaling pathway. But either way, you can see that the phospho prefix and the inositide prefix correspond with the inositol and the phospholipid prefixes that we see here. And so although these are 2 different words, you can see how they're related to one another and referring to the same exact pathway. However, moving forward in our Clutch Prep Biochemistry course, we're actually going to refer to this pathway as the Phosphoinositide pathway or the PSP pathway for short.
And so this phosphoinositide signaling pathway or PSP pathway, again is another classic example of a GPCR signaling pathway. And the PSP pathway actually mediates a wide variety of hormonal effects that include the hormones epinephrine, angiotensin, vasopressin, and much more that are not listed here. However, the main takeaway here is that depending on the exact hormone, the final function of this PSP pathway or the final cell response can actually vary. And so the PSP pathway actually has many, many different functions that could include blood platelet and injured cell signaling to stimulate growth and the injury repair process.
Now phosphoinositide signaling or the PSP pathway really requires these 5 components that you can see down below in our image right here. And so if we take a look down below at this image, what you'll notice is that we have these yellow numbers to label each of these 5 components in the PSP pathway. And we'll talk a lot more about each of these 5 components as we move forward in our course. But of course, the first major component in the PSP pathway, which of course we know is a GPCR signaling pathway, is going to be the GPCR itself. Now, rather than being a beta-adrenergic GPCR like what we saw in the adenylate cyclase GPCR signaling pathway, here in the PSP pathway we have an alpha-adrenergic GPCR, and so that is one major difference between the 2 GPCR pathways.
Now, of course, the second major component of a PSP pathway is going to be the heterotrimeric G protein here, which still has the alpha, beta, and gamma subunits just as we saw it before. And, of course, we know that the G proteins are going to be associated with G protein-coupled receptors or GPCRs. And I'm not exactly sure why they decided to use the Q here in this notation, but this is something that you'll commonly see throughout your textbooks and throughout your practice problems. And so you need to know that GQ is the abbreviation that's referring to the G protein specifically in the PSP pathway.
Now the 3rd component that we have here is the effector enzyme called phospholipase C or PLC for short. So we can go ahead and label this as PLC. And of course, we know that the effector enzyme is responsible for generating secondary messengers, and we'll talk more about the secondary messengers later in our course. But the substrate for the PLC is this molecule that you see right here, which is actually our representation of a glycerophospholipid. More specifically, it's the glycerophospholipid Phosphatidylenositol 4,5-bisphosphate, or as you could see, PIP2. And so, you can see these 2 phosphate groups here in position 4,5 and this phosphate group that you see here is actually representing the glycerophospholipid bond here. And so this is going to be our representation of PIP2 moving forward in our course. And again, we'll talk a lot more about each of these components moving forward in our course as well.
And so the 5th and final component here of PSP pathways is protein kinase C, which, of course, is going to be a kinase and is abbreviated as PKC. And so, protein kinase C is another component that we'll get to talk a lot more about, moving forward in our course. But these here are really the 5 main components that you guys should be familiar with as we move forward in our course, and we'll continue to talk more and more about their functions as we move forward in our course as well. And so for now, this here concludes our brief introduction to the phosphoinositide GPCR signaling pathway or the PSP pathway, and we'll continue to talk more about this moving forward. So I'll see you guys in our next lesson video.