b-cells are important component of the adaptive immune system b-cells when differentiated becomes plasma cell and the plasma cell is the source of secretory antibodies now the secretory antibodies against a pathogen might neutralize them or destroy them so diesel and b-cell receptor signaling is very important and interesting thing to know about so here is the portion of the surface of the B cell here we can see the membrane bound IgM which is the B cell receptor along with the B cell receptor many other co-receptor and other auxiliary receptors are there such as city twenty-one city 19 ta PA one and one of the most important component in this signaling in the B cell receptor complex is IG alpha and IG Peeta we would look at their function and how they take part in b-cell receptor signaling one by one now the antigen binds to CD 21 and the membrane bound IgM the membrane bound b-cell receptor of course now normally when there is no pathogen invasion or in a normal state the B cell receptors are kind of separated and segregated moving all around in the cell membrane kind of uniformly distributed but whenever it encounters a pathogen or a pathogenic antigen the B cell receptors kind of cluster in the lipid rafts of in specific subdomains of the B cell surface these lipid rafts are most important in terms of signaling many events many molecular and cellular events happen in these lipid traps and we would talk about that serially so one of the most important event is a receptor clustering now important kinase is such as Lin kinase can be part of these lipid raft and these Lin kinase can phosphorylate several components of the B cell receptor cluster so the B cell receptor cluster one of the most important part is IG alpha and IG beta now these are also molecules of IG superfamily and they have something called immune receptor tyrosine kinase based activation motif or items these items are site for phosphorylation by SRC family kinase such as the lean kind the limb kinase which is a SRC family kinase it can phosphorylate IG alpha and beta items and the phosphorylated items are actually docking site for adapter molecules such as blink now other kind of SRC family kinase is like psych can also bind to the phosphorylated IG alpha H beta and can trigger several molecular and cellular event which we would learn eventually now this blink adapter is very important in terms of signaling because it could serve like a platform for several signaling components to come in and set up a new signaling system for example map kinase signaling can be triggered if linked work like an adapter and as a result of the map kinase cascade the well-known map kinase cascade it might allow the binding of a p1 family transcription factor into the nucleus and allow the transcription of several important genes once a gene that is transcribed is known as CC + d1 no CC and d1 codes for cycling D and if we learned about cell cycle we know that cyclin D is super important for cell cycle progression because it it phosphorylates pRb and allow the e to F to bind to its target and give rise to cyclin e which is in turn important for replication and thereby procreation of the cell cycle so whenever cyclin D is produced as a result of antigen binding that means visa now can defied and form multiple different B cells so B cell proliferation can occur right now this is the outcome the cellular outcome of the signaling now let's talk about a different one we have already talked about that Lin kinase can phosphorylate the items of IG alpha n IG beta Lynn kinase can also phosphorylate the items of Sillitoe h1 and cd19 now these phosphorylated residues are actually docking hub for kinase is like pi3 kinase now pi3 kinase can convert pick two to pick three now pip3 is a docking site for a kt and a very important kinase now ATT has widespread function including cell survival including cell division and many others a kt can phosphorylate and inactivate several approve up optic molecules like packs and bad thereby the overall signaling can prevent the death of the B cell and indirectly it promotes the survival of the B cells the B cells upon antigen binding give rise to these whole downstream signal which would allow their division their survival and prevent they're built so this is how the peace cell signaling work the other arm of the signaling which is triggered by site kindnesses so I can activate direct phospholipase c gamma now phospholipase c gamma can cleave the tip to and give rise to ip3 and DHE the ip3 can in turn go and bind type its receptor in the endoplasmic reticulum which would allow calcium to be released in the cytoplasm an increase in calcium calcium level can be sensed by calcineurin which is a phosphatase now calcium ring can be phosphorylated now in fact is kind of restricted to the cytoplasm until calcineurin d phosphorylate that now the dephosphorylation of the infant allows the infant to be localized into the nucleus and give rise to gene transcription so in calcium-dependent way a variety of gene transcription Network is activated upon calcium binding so this is a very important function of b-cell receptor signaling I hope you enjoyed this video if you liked this video give it a big thumbs up and don't forget to like share and subscribe thank you