in the previous video we discussed about the diabetes mellitus and its types if you want to watch that video first the link is in the description now in this video we'll be discussing about the insulin signaling pathway this pathway regulates blood glucose levels and we know insulin decreases blood glucose levels and it must be noted here it is the glucagon which is the antagonist of insulin and if we see what this pathway does the insulin pathway basically mediates the uptake of glucose molecules from blood where glute4 channels the signaling molecule in this pathway is insulin
and the signaling receptor is insulin receptor which is a class of receptor tyrosine kinase molecules and the major important kinase molecule in this pathway is protein kinase b or akt now let's get to the pathway in detail here in this diagram we see we have the plasma membrane of the cell it has got insulin receptor in the form of monomoles embedded in the plasma membrane like we have two monomoles here the insulin receptor monomer has got one beta subunit that gets into the cell through membrane and to it we have extracellular alpha subunit bind as
shown in the diagram and we also have pip2 molecule bound to the cell membrane as shown in the diagram now to start a pathway we have insulin molecules present outside of the cell the insulin molecules comes in and binds on the alpha subunit of receptor as shown in the animation this ligand binding or the insulin binding drives the dimerization of insulin receptor as shown in the diagram and from this dimerization we get the intracellular cross phosphorylation of tyrosine domains on beta subunit of receptor now from here the downstream molecules are recruited and activated first of
all the irs molecule comes in and binds with activated receptor as shown in the diagram then this activated irs molecule recruits and activates the p85 subunit of pi3 kinase which in turn recruits the p110 subunit of pi3 kinase that is catalytic unit or pi3 kinase so we have now fully activated pi3 kinase and this activated pi3 kinase acts on pip2 and converts it into pip3 as shown in the animation and furthermore this pip3 activates the membrane mount pdk-1 molecule and other kinases now from here we have the inactive pkb or akt molecule so in order
to activate the pkb molecule it's first are regulated towards the plasma membrane and here it's acted upon by pdk1 molecule and this pdk-1 molecule phosphorylates the akt3onin residue at 308 which partially activates the akt protein then we also have the pdk2 molecule which phosphates akt and serine 473 residue that completely activates the akt protein now let's keep the activated akt protein here for some time on the other hand we have the glute4 vesicle which needs to be translocated to the plasma membrane for fusion but its translocation is inhibited by as160 protein it inhibits the translocation
of skeletal vesicle towards the plasma membrane but once we have akt activated by insulin pathway the akt postulates the as1 c0 at threonine 642 and serene 588 thereby inhibiting its activity so when as1 ck0 is inhibited the glute4 vesicle is easily translocated to the plasma membrane for fusion and we get the glut4 channels in the plasma membrane as shown in the diagram and these channels will then uptake the glucose molecules from blood thereby decreasing the blood glucose levels on the other hand we have the gsk3 molecule it inhibits the glycogen synthesis so we need to
inhibit this gsk3 molecule so that glycogen synthesis will go on and here it is done by the akt molecule also the akt molecule emits the gsk3 molecule thus driving the glycogen synthesis again furthermore we see the akt also activates the amp or c1 protein which inhibits the irs protein in a negative feedback loop so in nutshell we see the insulin pathway mediates the uptake of glucose from blood via glut4 channels and also ramps up the glycogen synthesis within the cell so this is all about the insulin signaling pathway i hope you liked the video if
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