Apoptosis (Programmed Cell Death)

00:11:10
https://www.youtube.com/watch?v=aemXc6AtpR0

Summary

TLDRApoptosis, or programmed cell death, is a fundamental cellular process occurring in humans and other organisms. It plays a significant role in vital biological functions such as embryonic development, where it helps shape structures like fingers, and in the immune system to prevent autoimmunity by eliminating self-reactive T-cells. Damaged, cancerous, or infected cells might also undergo apoptosis to protect overall body integrity. The video explores three primary mechanisms triggering apoptosis: the intrinsic pathway, the extrinsic pathway, and the apoptosis-inducing factor (AIF). The intrinsic pathway is triggered from within the cell, often involving mitochondria and proteins like Bax, Bcl-2, and cytochrome C, which result in the activation of caspases that dismantle cellular components and DNA. The extrinsic pathway begins outside the cell and involves "death receptors" interacting with immune cells, leading to internal signaling cascades that initiate cell death. Finally, the AIF mechanism stands out by not involving caspases; instead, it's triggered by neuronal cells releasing AIF to enter the nucleus, where it damages DNA, concluding the cell's life cycle. Apoptosis thus ensures proper development and maintenance of health by managing cell populations and eliminating potential cellular threats.

Takeaways

  • 🧬 Apoptosis is a programmed cell death crucial for development and health.
  • 👶 It helps shape body parts during embryonic development, like fingers and toes.
  • 🛡️ In the immune system, it eliminates self-reactive T-cells to prevent autoimmunity.
  • 💥 Damaged, cancerous, or infected cells undergo apoptosis for body protection.
  • ⚙️ Intrinsic pathway involves mitochondrial proteins like cytochrome C in cell death.
  • 🔗 Extrinsic pathway starts with external signals binding to death receptors on cells.
  • 🧪 Apoptosis-inducing factor (AIF) can trigger apoptosis without caspases.
  • 🧠 Neurons might use AIF for apoptosis, leading to DNA being destroyed.
  • 🔍 Understanding apoptosis is key in therapies against diseases like cancer.
  • 📚 Apoptosis ensures controlled cellular turnover and organismal health.

Timeline

  • 00:00:00 - 00:05:00

    Apoptosis, or programmed cell death, is a natural process that occurs in the cells of multicellular organisms, including humans. It is crucial during embryonic development and the development of the immune system. For example, apoptosis helps shape fingers and toes by eliminating cells in between. In the immune system, T-cells undergo apoptosis in the thymus if they bind to self-antigens, preventing autoimmunity. Additionally, apoptosis prevents damage by eliminating harmful, damaged, or cancerous cells.

  • 00:05:00 - 00:11:10

    Apoptosis can occur via three common mechanisms: intrinsic, extrinsic, and apoptosis-inducing factor (AIF) pathways. The intrinsic pathway starts within the cell, particularly in the mitochondria, and involves the release of cytochrome c and activation of caspase-9, leading to cell death. The extrinsic pathway is triggered by external signals binding to death receptors on the cell surface, activating caspase-8, and resulting in cell death. The AIF pathway does not involve caspases but relies on AIF release from the mitochondria to the nucleus to destroy DNA, often seen in neurons. These mechanisms ensure the removal of potentially harmful cells.

Mind Map

Video Q&A

  • What is apoptosis?

    Apoptosis is a programmed cell death process that leads to the orderly and efficient removal of damaged cells.

  • Why is apoptosis important during embryonic development?

    Apoptosis is crucial during embryonic development to form structures, such as fingers and toes, by removing unnecessary cells.

  • How does apoptosis contribute to immune system development?

    In immune system development, apoptosis removes T-cells that could attack the body's own cells, preventing autoimmunity.

  • What triggers apoptosis in damaged cells?

    Apoptosis in damaged cells can be triggered by intrinsic and extrinsic pathways involving specific proteins and signals.

  • What role does the protein Bax play in apoptosis?

    The protein Bax promotes apoptosis by binding to mitochondrial membranes, causing cytochrome C release that activates cell death processes.

  • How does the intrinsic pathway of apoptosis function?

    The intrinsic pathway triggers apoptosis internally by mitochondrial cytochrome C release, leading to caspase activation that degrades cell components.

  • What is the extrinsic pathway of apoptosis?

    The extrinsic pathway involves external signals from other cells binding to death receptors, activating internal processes that lead to cell death.

  • What is apoptosis-inducing factor (AIF)?

    AIF is a protein that, when released from mitochondria upon cell damage, enters the nucleus and induces DNA degradation, leading to cell death.

  • How does the extrinsic pathway differ from the intrinsic pathway?

    The extrinsic pathway starts with external signals, while the intrinsic pathway is triggered by internal cell damage.

  • What cells utilize the AIF mechanism for apoptosis?

    Neurons can undergo apoptosis via AIF, where the factor promotes DNA destruction without involving caspases.

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  • 00:00:00
    apatow s-- is also known as programmed
  • 00:00:02
    cell death is a process that takes place
  • 00:00:05
    not only in the cells of our own body
  • 00:00:08
    but also the cells of other organisms as
  • 00:00:11
    well now what exactly is a pitocin why
  • 00:00:15
    does a pitocin actually take place and
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    how does a Patil is actually take place
  • 00:00:20
    these are the questions we're going to
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    address in this lecture and let's begin
  • 00:00:25
    with the what so what exactly is a
  • 00:00:28
    pitocin well it's a process a natural
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    process that takes place inside our own
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    cells and if the cell actually commits
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    to apatow sizz what it does is it will
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    follow a series of reactions that will
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    eventually kill that cell off so in a
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    way a pitocin is cell suicide now the
  • 00:00:50
    next question is why in the world would
  • 00:00:52
    a cell actually want to kill itself off
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    why would a cell want to commit suicide
  • 00:00:57
    well one of two reasons as it turns out
  • 00:01:01
    a pitocin is a normal process during
  • 00:01:05
    embryo logical development and it's also
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    normal process during the development of
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    our immune system so what exactly do we
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    mean well when the embryo is developing
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    inside the uterus of the mother to
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    actually form the fingers on the hand
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    and the toes on the feet apatow
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    sustained at relie between this between
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    the regions on the fingers to actually
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    form the fingers so the reason we go
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    from this to this is because of a
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    pitocin that takes place during normal
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    embryological development
  • 00:01:40
    now what about development of our immune
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    system well remember t-cells also known
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    as T lymphocytes mature and develop
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    inside the thymus so what happens inside
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    the thymus which is an organ found in
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    this section on the body inside the
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    thymus those T lymphocytes are tested
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    against self antigens remember self
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    antigens are proteins found on the
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    healthy cells of our body and if those T
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    lymphocytes bind onto these healthy self
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    antigens
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    then the binding process will initiate
  • 00:02:16
    Apatow psious and those t-cells will be
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    killed off the reason is if the t-cells
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    actually bind on to self antigens that
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    means those T lymphocytes will begin to
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    kill off the healthy cells of our body
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    and we don't want this we don't want to
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    cause a condition known as autoimmunity
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    and so what happens in the thymus we
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    eliminate those t-cells these immune
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    illogically insufficient t-cells by the
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    process of apoptosis so we see that
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    Apatow sious is a normal process that
  • 00:02:52
    takes place in development of the organ
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    systems and the structures of our body
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    now reason number two is basically to
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    prevent from that cell harming other
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    cells of our body so to destroy
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    dangerous agents that can harm the
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    healthy cells of our body for example
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    cancer cells infected cells or any type
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    of damaged cell will undergo apoptosis
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    to kill itself off so this is why what
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    about how how this Apatow sis actually
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    take place well there are three very
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    common mechanisms by which a petula
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    States
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    mechanism number one is called intrinsic
  • 00:03:35
    pathway mechanism number two is called
  • 00:03:37
    the extrinsic pathway and mechanism of
  • 00:03:41
    three involves a molecule known as a
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    pitocin inducing factor or AI F so let's
  • 00:03:48
    begin with the intrinsic pathway so in
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    this mechanism the process of cell death
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    initiates inside the cell itself in fact
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    it initiates inside the mitochondria as
  • 00:04:02
    we'll see in just a moment so let's
  • 00:04:05
    suppose the cell is damaged in some way
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    or form because remember a damaged cell
  • 00:04:11
    will undergo apoptosis so if the cell is
  • 00:04:14
    damaged what happens is the following
  • 00:04:17
    takes place so let's suppose we're
  • 00:04:19
    inside the mitochondria this is the
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    outer membrane of the mitochondria
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    this is the inner membrane of the
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    mitochondria along the inner membrane we
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    have these proteins known as cytochrome
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    C which are shown in red and on the
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    outer membrane of the mitochondria in
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    healthy cells we have a special type
  • 00:04:41
    protein known as bcl-2 now bcl-2 what it
  • 00:04:45
    does is it basically inhibits the
  • 00:04:48
    process of apoptosis from actually
  • 00:04:51
    taking place but if the cell is damaged
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    in some way or form what happens is
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    another type of protein is produced and
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    released and this protein is known as
  • 00:05:01
    Beck's ba X shown in purple so what
  • 00:05:05
    happens is once the cell is actually
  • 00:05:08
    damaged back AB acts moves on onto the
  • 00:05:11
    cell membrane of the mitochondria and
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    attaches next to this bcl-2 protein now
  • 00:05:18
    what Beck's does is it prevents the
  • 00:05:21
    bcl-2 protein from inhibiting apatow
  • 00:05:25
    --ss and backs also punctures the
  • 00:05:28
    membrane of the mitochondria so it
  • 00:05:30
    creates holes inside the outer membrane
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    and what happens is once the holes are
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    created cytochrome C detaches from the
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    membrane of the inner mitochondria and
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    move to the outside of that mitochondria
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    into the cytoplasm now once inside the
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    cytoplasm so these are the cytochrome C
  • 00:05:53
    molecules the cytochrome C attach it to
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    another type of protein known as a PA f1
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    and once they attach they form a special
  • 00:06:03
    structure known as a POTUS own now what
  • 00:06:06
    a POTUS own does is it basically goes on
  • 00:06:10
    and activates a special type of protease
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    protein known as caspase-9
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    and by activating caspase-9 we form a
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    complex known as the active caspase-9
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    complex and what this complex does is it
  • 00:06:27
    moves around the organelles of our bot
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    of the organelles of that cell and they
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    break down those organelles and
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    eventually they break down the DNA
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    inside that cell and that causes the
  • 00:06:41
    death of that cell and once the cell
  • 00:06:43
    actually dies off some type of
  • 00:06:45
    phagocytic cell for example a macrophage
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    swims by and engulfs that cell and so
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    this is one mechanism by which this
  • 00:06:55
    process of apoptosis takes place and it
  • 00:06:58
    involves this special type of active
  • 00:07:01
    protein known as
  • 00:07:02
    caspase-9 now this entire process takes
  • 00:07:07
    place inside that cell it initiates and
  • 00:07:10
    takes place inside the cell what about
  • 00:07:13
    the extrinsic pathway well the major
  • 00:07:16
    difference between the intrinsic and the
  • 00:07:18
    extrinsic pathway is the origin in the
  • 00:07:21
    extrinsic pathway is outside of the cell
  • 00:07:24
    so in this mechanism the signal
  • 00:07:27
    molecules are originating outside of the
  • 00:07:30
    cell and they stimulate that cell to
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    commit suicide inside that cell so it
  • 00:07:36
    begins on outside but then it takes
  • 00:07:39
    place a pitocin takes place on the
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    inside so healthy cells contain special
  • 00:07:46
    integral membrane proteins known as deaf
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    receptors and that can bind
  • 00:07:52
    complementary molecules known as deaf
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    activators so to see what we mean let's
  • 00:07:58
    take a look at the following molecule so
  • 00:08:00
    let's suppose this blue cell is our
  • 00:08:03
    infected cell and that in fact itself
  • 00:08:06
    has a special membrane protein known as
  • 00:08:08
    the death receptor and this is some
  • 00:08:12
    other type of cell let's suppose it's
  • 00:08:14
    some type of immune cell for example the
  • 00:08:17
    cytotoxic T cell now the cytotoxic T
  • 00:08:21
    cell has a special membrane protein
  • 00:08:23
    known as the death activator and so what
  • 00:08:26
    happens is when they actually bind on
  • 00:08:29
    the outside that will initiate some type
  • 00:08:32
    of internal process that will activate a
  • 00:08:36
    cast space protein but this caspase
  • 00:08:39
    protein is slightly different than
  • 00:08:41
    caspase-9 we call it caspase-8 but it's
  • 00:08:45
    still protease and what that means is
  • 00:08:48
    once we act
  • 00:08:49
    the caspase-9 inside the cell that
  • 00:08:53
    caspase I'm sorry caspase-8 once we
  • 00:08:56
    activate the caspase-8 it will go on to
  • 00:08:59
    basically destroy the organelles and
  • 00:09:02
    instructors inside the cell as well as
  • 00:09:04
    the DNA inside the nucleus of that cell
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    and that will eventually lead to the
  • 00:09:09
    death of that cell and once the cell
  • 00:09:12
    dies once again a macrophage or another
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    phagocytic cell can swim by and Gulf
  • 00:09:18
    that that cell and that will prevent
  • 00:09:20
    that infected cell from actually
  • 00:09:22
    destroying other healthy cells of our
  • 00:09:25
    body now what about the final mechanism
  • 00:09:28
    so notice in the intrinsic pathway and
  • 00:09:31
    the extrinsic pathway we both used a
  • 00:09:33
    category of protease proteins known as
  • 00:09:37
    caspase the major difference between the
  • 00:09:40
    final mechanism and these two mechanisms
  • 00:09:42
    is that this does not actually include a
  • 00:09:45
    caspase protein it includes its own
  • 00:09:48
    molecule known as a pitocin inducing
  • 00:09:52
    factor or AI F so the final mechanism of
  • 00:09:57
    apatow PSA's involves using a pitocin
  • 00:10:00
    inducing factor a RF to actually
  • 00:10:03
    initiate the process of apoptosis this
  • 00:10:06
    process does not use caspases so what
  • 00:10:10
    exactly happens well AI F basically is
  • 00:10:14
    located inside the inter membrane space
  • 00:10:17
    between the two membranes of the
  • 00:10:19
    mitochondria and if the cell is actually
  • 00:10:23
    damaged in some way what happens is this
  • 00:10:26
    AI F molecule is released from the
  • 00:10:30
    mitochondria it travels into the
  • 00:10:33
    cytoplasm and then it moves into the
  • 00:10:36
    nucleus of that cell it binds on to the
  • 00:10:39
    DNA of that cell and ultimately destroys
  • 00:10:42
    that DNA and that causes the death of
  • 00:10:46
    that cell so ultimately this is
  • 00:10:48
    basically done by cells such as neurons
  • 00:10:51
    so nerve cells in our body can commit
  • 00:10:54
    apatow psious via this process by using
  • 00:10:57
    the Apatow siz inducing factor so these
  • 00:11:01
    are the three common methods by which
  • 00:11:03
    our
  • 00:11:03
    cells can naturally commit cell suicide
  • 00:11:06
    a process known as apoptosis
Tags
  • Apoptosis
  • Cell Death
  • Embryonic Development
  • Immune System
  • Intrinsic Pathway
  • Extrinsic Pathway
  • Caspases
  • Mitochondria
  • AIF
  • Programmed Cell Death