February 8, 2023

this video describes the molecular mechanism of insulin secretion by the pancreatic beta cell

Hi in this video we will talk about how pancreatic beta-cell secretes insulin we would understand the physiological context and the molecular mechanism by which insulin secretion takes place so let’s start here is our pancreas if you zoom in to our pancreas and try to take a cross-section the pancreas would somewhat look like this and if we look at these green cells

Which are the depiction of beta cells now these beta cells secrete influent there are other cell types also present in the pancreas which we are not focusing right now but let’s just focus on the pancreatic beta cells and try to understand that how pancreatic beta cell secret ensuing note that pancreatic beta-cell are very few in number compared to the other cell

Types present here now the pancreatic beta cell has specific gene expression pattern it expresses the is one gene which is located at the chromosome 11 p 15.5 locus now this particular gene encodes for insulin insulin is a protein easiest hormone so insulin has to be or the precursor form of the insulin has to be encoded by the gene and it is i&s gene which

Encodes the insulin now let’s look at this process in bit more details that how insulin synthesis or insulin biogenesis takes place so from the insulin gene look at in the eleventh chromosome the mrna would be produced now this mrna once transcribed from the insulin gene it would be moving out through the nuclear pore and on the top of the rough endoplasmic reticulum

The ribosomes which is sitting there they would convert the mrna i mean they would translate the mrna into peptide now these peptides at the precursor from form of the insulin now these peptides are going to be packaged inside the endoplasmic then it would move to golgi from there it would be mobilized as a secretory vesicle so first it is packaged in endoplasmic

Reticulum then further it would be it would be moved to the cells secretory pathway via the golgi apparatus and it would be almost ready to secrete now inside the secretory vesicle there are specific enzymes such as hormone converters and carboxy peptidase which would cleave the sea peptide of the ensuing in this case the sea peptide is depicted as an orange bead of

String now the insulin hormone would be now packaged inside these vesicles secretory vesicles and ready to be secreted now since this is gene is expressing most of the time insulin is always ready insulin is ready and it is queen packaged inside the vesicle ready to be secreted but without a particular context insulin is not secreted by the pancreatic beta-cell so

What is the context here so insulin would be only secreted when the glucose level is high and it would try to divert the glucose inside the cells such that the cells can utilize the glucose that’s the function of the insulin now how does at the first place the pitcher cell knows that there is ample amount of glucose present in the bloodstream the answer is simple

Right insulin is packaged in the vesicle but waiting for a signal to be discharged and the signal is basically the blood glucose level so let’s say you have it in a donor tasty doughnut and the doughnut will be broken down and it’s monosaccharides lot of glucose would be actually absorbed in the intestine and from the intestine the glucose would be elevated in

Your bloodstream but still it doesn’t answer that how pancreatic cell would understand that glucose elevation took place in the bloodstream so pancreatic beta-cells specific channels or transporters i would say these are called blue to glucose transporter 2 here depicted as this blue on channels this glute 2 would allow glucose to enter from the blood vessel now

The pancreas has many blood vessels supplying blood flow in the pancreas so these glucose which is carried in the blood flow would also get inside the pancreatic beta-cell and thereby it would trigger the secretion of insulin which are already packaged and ready inside the vesicle but let’s just delve into the details of the molecular mechanism so let’s see the

Process again what happens when glucose is absent what happens when glucose is present when glucose is absent in absence of glucose the pancreatic beta-cell is in a hyper polarized state in that situation one particular potassium channel which is atp dependent is 1 as a result potassium leaks out and the cell is hyperpolarized but when buca’s comes in glucose gets

Converted to glucose 6-phosphate entered like all is his pathway and from glycolysis pathway we know there would be atp production and it eventually the glucose would be also used to produce atp but when there is glucose there would be atp and this atp would eventually inhibit this potassium channel or the leaky potassium channel so once potassium is not moving

Out the cells would be rather going to a depolarized state in this situation several calcium channel also open in the pancreatic beta-cell which allows calcium influx inside the cell now calcium helps in vesicle docking events these vesicles which are filled with insulin are ready they are packaged with insulin they are waiting for a trigger to be released and

That trigger for release is the elevation of the camp calcium which is due to elevation of glucose level in the pancreatic beta-cell now the calcium would help to modulate the snare complexes and allow the fusion of this vesicle with the membrane which would allow the insulin to be secreted and once the insulin is secreted it is ready to perform its job but how

Does insulin perform its job do you want to know indians inertia you know that you have to watch my second video about how in fluid is the mechanism of insulin action action so i hope this video was informative this video was helpful if you liked this video give it a quick thumbs up and don’t forget to like share and subscribe and do let me know in the comment how

Do you like my videos your comment give me so much positive motivation to make more videos thank you

Transcribed from video
Insulin secretion: molecular mechanism of insulin synthesis and secretion By Animated biology With arpan