MT28Lec-Sodium pumps, Cell signsling, cytoskeleton, and cell cycle

Na+ PUMPS

Also known as Sodium Potassium ATPase or Sodium Potassium Pump, it is responsible for maintaining the membrane potential of the cell by pumping out sodium and carrying in potassium using ATP.

K+ LEAK CHANNELS

Non-specific channels that allow potassium to move freely across the membrane, creating the negative resting membrane potential.

MEMBRANE POTENTIAL

The difference in electrical charge between the inside and outside of the cell membrane. Outside of the cell is positive, while inside is negative.

NEURONAL COMMUNICATION

The process by which neurons interact with each other through electrical signals.

ACTION POTENTIAL

A rapid change in membrane potential triggered by depolarization of the cell membrane, causing a sudden influx of Na+ ions.

VOLTAGE-GATED Na+ CHANNEL

Channels that open when the cell membrane is depolarized, allowing Na+ ions to enter and causing the action potential.

CONFORMATIONS OF Na+ CHANNEL

The different states of the Na+ channel, including closed, open, and inactivated.

SPREAD OF ACTION POTENTIAL

The sequential spread of the action potential along the neuron, with Na+ channels opening, temporarily inactivating, and then closing again.

SYNAPSES

The junctions between neurons, including the synaptic cleft (gap between neurons), presynaptic cell (transmitting neuron), and postsynaptic cell (receiving neuron).

RELEASE OF NEUROTRANSMITTERS

The process triggered by voltage-gated Ca+ channels, causing fusion of synaptic vesicles and release of neurotransmitters.

TYPES OF NEUROTRANSMITTERS

Excitatory neurotransmitters, such as acetylcholine and glutamate, cause depolarization of the cell. Inhibitory neurotransmitters, such as GABA and glycine, make it harder for the cell to be depolarized.

Cell Signaling

The process of converting signals between cells.

Extracellular Signaling

Communication between cells using signaling molecules.

Endocrine Signaling

Signaling throughout the whole body using hormones.

Paracrine Signaling

Signaling within a local area using local mediators.

Autocrine Signaling

Self-stimulating signaling where the signaling cell is also the target cell.

Neuronal Signaling

Long-distance signaling using neurons and neurotransmitters.

Contact-Dependent Signaling

Signaling through direct physical contact between cells.

Target Cell Response

The response of a target cell to a signaling molecule.

Receptors

Proteins that are activated by specific signal molecules.

Cell Surface Receptors

Receptors located on the surface of the cell that detect extracellular signaling molecules.

Intracellular Receptors

Receptors found inside the cell, often in the nucleus, that detect small hydrophobic signaling molecules.

Intracellular Signaling Pathways

Pathways that relay, amplify, integrate, and distribute signals within the cell.

Positive Feedback

Feedback loop that enhances the response to a signal.

Negative Feedback

Feedback loop that diminishes or stops the response to a signal.

Molecular Switches

Intracellular signaling molecules that can stimulate or suppress cellular responses.

Proteins Activated or Inactivated by Phosphorylation

Proteins that are controlled by the addition or removal of phosphate groups.

GTP-Binding Proteins

Proteins that can be in an active or inactive state depending on the presence of GTP.

Protein Kinase

Enzyme that adds phosphate groups to proteins.

Protein Phosphatase

Enzyme that removes phosphate groups from proteins.

GDP

Guanosine diphosphate, a molecule that is attached to GTP-binding proteins in their inactive state.

GTP

Guanosine triphosphate, a molecule that is bound to GTP-binding proteins in their active state.

GTP-hydrolyzing

The process of converting GTP to GDP by hydrolyzing the terminal phosphate group.

Monomeric GTPase

A type of GTP-binding protein that is regulated by guanine nucleotide exchange factors (GEFs) and GTPase-activating proteins (GAPs).

Guanine nucleotide exchange factors (GEFs)

Proteins that promote the exchange of GDP for GTP on GTP-binding proteins.

GTPase-activating proteins (GAPs)

Proteins that promote the hydrolysis of GTP to GDP on GTP-binding proteins.

Trimeric GTP-Binding Proteins

Also known as G-proteins, these proteins are composed of three subunits (α, β, and γ) and are activated by G-protein coupled receptors.

G-protein coupled receptors

Cell surface receptors that activate G-proteins and are the largest family of cell surface receptors.

Ion-channel-coupled receptors

Cell surface receptors that alter the membrane potential by opening or closing ion channels.

G-protein targets

Cellular components that are affected by the activation of G-proteins, including ion channels and membrane-bound enzymes.

Enzyme-coupled receptors

Cell surface receptors that activate themselves or an associated enzyme, often in the form of dimers.

Cytoskeleton

An intricate network of protein filaments that extends throughout the cytoplasm and provides structural support to the cell.

Intermediate filaments

One of the three types of protein filaments that make up the cytoskeleton, characterized by their fibrous composition and tensile strength.

Microtubules

One of the three types of protein filaments that make up the cytoskeleton, characterized by their tubular structure and involvement in cell movement and division.

Actin filaments

One of the three types of protein filaments that make up the cytoskeleton, characterized by their thin and flexible structure and involvement in cell shape changes and movement.

Nuclear lamina

A meshwork of intermediate filaments that surrounds the nucleus and provides structural support.

Plectin

An accessory protein that helps connect different cytoskeletal elements together.

Epidermolysis bullosa simplex

A disease caused by mutations in the keratin genes, leading to abnormal formation of keratin filaments and vulnerability of the skin to mechanical injury.

Amyotrophic Lateral Sclerosis (ALS)

Also known as Lou Gehrig's disease, it is characterized by the abnormal accumulation of neurofilaments in motor neurons, leading to axon degeneration and muscle weakness.

Progeria

A condition characterized by defects in the nuclear lamin, causing affected individuals to age prematurely. It is hypothesized to be related to DNA damage and inefficient cell division due to nucleus defects.

Microtubules

Long and relatively stiff cytoskeletal filaments that have a crucial organizing role in all eukaryotic cells. They create a system of tracks within the cell for the transport of organelles, vesicles, and large proteins.

Centrosome

The major organizing center of microtubules in non-dividing cells, composed of a pair of centrioles. It serves as the starting point of growth for microtubules.

Dynamic Instability of Microtubules

The ability of microtubules to rapidly grow and shrink. They can be stabilized by attaching to a protein or cell structure, forming stable microtubules.

GTP hydrolysis

The process of hydrolyzing GTP (guanosine triphosphate) by tubulin dimers, which affects the growth and stability of microtubules.

Motor Proteins

Proteins that carry cargo along microtubules. Kinesin moves towards the plus end, away from the centrosome, while dynein moves towards the minus end, going back to the centrosome.

ATPase activity

The ability of motor proteins to hydrolyze ATP (adenosine triphosphate) into ADP (adenosine diphosphate), providing the energy for their movement along microtubules.

Drugs Affecting Microtubules

Drugs that prevent microtubule assembly and disassembly, thereby preventing cell division. They can be used to stop or treat aggressive cancers.

Actin

Cytoskeletal filaments concentrated along the cell periphery, used for movement of the cell surface. They are thinner, more flexible, and usually shorter than microtubules.

Cell Cortex

The scaffold that holds the cell membrane to the cell body, where actin is found in bundles and networks.

Actin Monomers

The building blocks of actin filaments, which can grow and shrink in the cell by utilizing ATP (adenosine triphosphate). They have a plus and minus end and can hydrolyze ATP to ADP.

Actin

A protein that forms filaments and plays a role in cell movement and structure.

ATP

Adenosine triphosphate, a molecule that provides energy for cellular processes.

ADP

Adenosine diphosphate, a molecule that is produced when ATP is used and provides less energy.

Actin monomers

Individual units of actin that can assemble into filaments.

Treadmilling

The process in which actin filaments grow at one end while shrinking at the other end, resulting in a constant overall length.

Actin-binding proteins

Proteins that regulate the behavior of actin, including controlling polymerization and promoting movement.

Thymosin and profilin

Actin-binding proteins that prevent actin polymerization.

Formins and actin-related proteins (ARPs)

Actin-binding proteins that promote actin polymerization.

Bundling protein

A type of actin-binding protein that creates bundles or groups actin filaments together.

Cross-linking protein

A type of actin-binding protein that promotes cross-linkages between actin filaments.

Myosin motor protein

A protein that interacts with actin and promotes movement.

Severing proteins

Proteins that can break actin filaments, allowing for their destruction.

Phalloidin

A substance that stabilizes actin filaments and prevents them from disassembling.

Cytochalasin and Latrunculin

Substances that prevent actin polymerization, freezing cell movements.

Cell cycle

The process of cell duplication, involving the duplication of cellular contents and division into two daughter cells.

Eukaryotic cell cycle phases

The different phases of the cell cycle, including M-phase (mitosis and cytokinesis) and interphase (G1, S, and G2 phases).

Cell cycle control system

A network of regulatory proteins that ensures the proper sequence of key processes in the cell cycle.

Checkpoints

Pauses in the cell cycle at certain transition points to ensure each process has been completed before the next one begins.

Cyclin-dependent protein kinases (Cdks)

The major protein kinases that control the cell cycle and are activated by cyclin proteins.

Cyclin

Proteins that regulate Cdks and control cell-cycle events, such as entry into S phase or M phase.

Anaphase-promoting complex or cyclosome (APC/C)

A complex that marks cyclins for degradation, leading to inactivation of cyclin-Cdk complexes and the end of mitosis.

Inhibitory kinase

A kinase that adds inhibitory phosphates to cyclin-Cdk complexes, inhibiting their activity.

Activating phosphatase

A phosphatase that removes inhibitory phosphates from cyclin-Cdk complexes, activating their activity.

Cdk inhibitor proteins

Proteins that block the assembly and activity of cyclin-Cdk complexes.

Cdk inhibitors

Proteins that can inhibit the activity of cyclin-dependent kinases (Cdks).

p27

A specific Cdk inhibitor that binds to an active cyclin-Cdk complex, preventing the Cdk from phosphorylating target proteins necessary for transitioning from G1 to S phase in the cell cycle.

Pauses in the cell cycle

Periods of temporary halt in the progression of the cell cycle, which can occur due to various factors.

G1-to-S transition

The transition from the G1 phase to the S phase in the cell cycle, which is regulated by Cdk inhibitors to prevent entry into S phase and DNA replication.

G2-to-M transition

The transition from the G2 phase to the M phase in the cell cycle, which is inhibited by suppressing the activation of M-Cdk.

APC/C

An abbreviation for Anaphase-Promoting Complex/Cyclosome, a protein complex involved in the regulation of mitotic exit by promoting the degradation of M cyclin.

Events in G1 phase

Inactivation of cyclins, stimulation by mitogens, and cell build-up are important events that occur in the G1 phase of the cell cycle.

Mitogens

Extracellular signals produced by other cells that stimulate the synthesis of G1 and G1/S cyclins, kickstarting DNA synthesis and chromosome duplication.

Retinoblastoma (Rb) protein

A protein that represses genes for cell proliferation and is present in all nuclei.

p53 protein

A protein that is increased if DNA damage is present and promotes the production of the Cdk inhibitor protein p21.

DNA damage

Damage to the DNA molecule that can pause the cell cycle in G1 and trigger protein kinases that activate p53.

Pre-replicative complex (preRC)

A complex formed during DNA replication initiation, consisting of the Origin Recognition Complex (ORC), Cdc6, and S-Cdk.

Origin Recognition Complex (ORC)

A protein complex found at DNA replication origins.

Cdc6

A protein that helps load DNA helicase onto the DNA during DNA replication initiation.

S-Cdk

A cyclin-dependent kinase that is activated during S phase and promotes the assembly of replication fork proteins for DNA synthesis.

Replication fork

The site where DNA replication occurs, consisting of two unwound DNA strands.