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Master’s-Level Cell Biology & Advanced Molecular Biology Notes 1. Definition JAKā€“STAT signaling is a relatively direct mechanism by which extracellular signals, particularly cytokines, interferons, growth factors, and some hormones, regulate gene expression. The pathway consists of two major components: Unlike RTK signaling, where receptor kinase activity is intrinsic to the receptor, many JAKā€“STAT receptors lack intrinsic kinase activity and depend on receptor-associated JAKs. Core pathway 2. Why Is It Called JAKā€“STAT? JAK Janus kinase Named for the Roman god Janus because JAK proteins contain important kinase-related domains with distinct regulatory functions. STAT Signal Transducer and Activator of Transcription STAT proteins perform two roles: Thus, theRead More →

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Master’s-Level Cell Biology & Advanced Molecular Biology Notes 1. Definition Receptor tyrosine kinases (RTKs) are a major family of cell-surface transmembrane receptors that convert extracellular signals into intracellular responses by activating protein tyrosine kinase activity. RTKs regulate: Important RTKs include receptors for: 2. Basic RTK Structure A typical RTK contains three major regions: Major components 3. Important Difference from GPCRs RTKs differ fundamentally from GPCRs. Feature GPCR RTK Transmembrane segments 7 Usually 1 Main signaling partner Heterotrimeric G protein Protein/adaptor signaling complexes Intrinsic kinase activity No Usually yes Major phosphorylation Various downstream proteins Tyrosine residues Major pathways cAMP, IP3/DAG RASā€“MAPK, PI3Kā€“AKT, PLCĪ³ Typical function BroadRead More →

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Master’s-Level Cell Biology & Advanced Molecular Biology Notes 1. Definition G-protein-coupled receptors (GPCRs) are a large family of cell-surface receptors characterized by seven transmembrane Ī±-helical domains that transduce extracellular signals into intracellular responses through heterotrimeric G proteins and associated signaling pathways. GPCRs respond to diverse ligands including: They regulate: 2. Basic GPCR Architecture A GPCR contains: The seven helices are conventionally numbered: TM1 ā†’ TM7 3. The Heterotrimeric G Protein The classical signaling partner of a GPCR is a heterotrimeric G protein consisting of: The GĪ± subunit binds guanine nucleotides: 4. The Central GPCR Signaling Cycle The core mechanism is: 5. Inactive State In theRead More →

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Master’s-Level Cell Biology & Advanced Molecular Biology Notes 1. Definition A receptorā€“ligand interaction is the specific, usually reversible binding of a signaling molecule (ligand) to a complementary receptor, resulting in a conformational or organizational change that initiates or modifies cellular signaling. General principle The ligand provides the information, while the receptor detects and converts that information into a cellular response. 2. What Is a Ligand? A ligand is a molecule that binds specifically to a receptor. Examples include: Peptides and proteins Small molecules Lipid-derived molecules Gases Extracellular matrix ligands 3. What Is a Receptor? A receptor is a macromolecular sensor, usually a protein, that recognizesRead More →

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Master’s-Level Cell Biology & Advanced Molecular Biology Notes 1. Definition Matrix metalloproteinases (MMPs) are a family of zinc-dependent proteolytic enzymes that cleave extracellular-matrix (ECM) proteins and other extracellular or cell-associated substrates. They are major regulators of: MMPs are not simply “matrix-destroying enzymes”; they are regulated molecular remodeling enzymes that alter the biochemical and mechanical information contained within the ECM. 2. Basic Reaction At a simplified level: MMP-mediated cleavage can therefore alter both structure and cell signaling. 3. Why Are They Called Metalloproteinases? The term has three components: Matrix Many substrates are components of the extracellular matrix. Metallo Their catalytic activity requires a metal ion, primarilyRead More →

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Master’s-Level Cell Biology & Advanced Molecular Biology Notes 1. Definition Extracellular matrix (ECM) remodeling is the continuous, regulated process of degradation, modification, synthesis, reorganization, and mechanical restructuring of extracellular-matrix components. It allows tissues to change their: ECM remodeling is not simply ECM degradation; it is a dynamic balance between matrix deposition, degradation, cross-linking, reorganization, and cell-mediated mechanical forces. 2. Major Components of the ECM The ECM consists broadly of: Fibrous proteins Adhesive glycoproteins Proteoglycans and glycosaminoglycans 3. Why Is ECM Remodeling Necessary? ECM remodeling is required for: It also contributes to pathological processes such as: 4. Basic Concept The ECM exists in a dynamic equilibrium.Read More →

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Master’s-Level Cell Biology & Advanced Molecular Biology Notes 1. Definition Laminins are large, multifunctional extracellular matrix glycoproteins that are major structural and signaling components of basement membranes. They regulate: Laminins are major basement-membrane organizers that connect extracellular matrix architecture with cell-surface receptors and intracellular signaling. 2. Basic Structure Laminins are heterotrimeric glycoproteins composed of three genetically distinct chains: These chains associate to form a characteristic cross-shaped molecule. A laminin molecule therefore contains: 1 Ī± + 1 Ī² + 1 Ī³ chain 3. Laminin Gene Families Humans possess multiple laminin chain genes: These can combine to form numerous laminin heterotrimers. Examples: The numbering indicates: Ī±Ī²Ī³ chainRead More →

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Master’s-Level Cell Biology & Advanced Molecular Biology Notes 1. Definition Fibronectin (FN) is a large, multifunctional extracellular matrix glycoprotein that plays a central role in: Fibronectin acts as a molecular bridge between cells and the extracellular matrix. Fibronectin links ECM components such as collagen to cell-surface integrins, thereby connecting extracellular matrix organization with intracellular cytoskeletal signaling. 2. Basic Structure Fibronectin is composed of two similar polypeptide subunits linked near their C-termini by disulfide bonds. It is therefore a disulfide-linked dimer. Each subunit contains multiple functional domains. 3. Fibronectin as a Modular Protein Fibronectin is a modular multidomain protein. It contains repeating structural modules known as:Read More →

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Master’s-Level Cell Biology & Advanced Molecular Biology Notes 1. Definition Collagen is the major structural protein of the extracellular matrix (ECM) and is the most abundant protein in the human body. It provides: Collagen is particularly important in: Collagen is not simply a structural scaffold; it is a dynamic signaling and mechanobiological component of the extracellular matrix. 2. Basic Molecular Organization The fundamental structural unit of fibrillar collagen is the triple helix. It consists of three polypeptide Ī±-chains wound around each other. Each chain has a characteristic repeating sequence: Glyā€“Xā€“Y where: 3. Why Glycine Is Essential The repeating sequence is approximately: Glyā€“Xā€“Yā€“Glyā€“Xā€“Yā€“… Glycine is theRead More →

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Master’s-Level Cell Biology & Advanced Molecular Biology Notes 1. Definition Integrins are heterodimeric cell-surface adhesion receptors that mediate interactions between cells and the extracellular matrix (ECM) and, in some cases, between cells and other cells. They are composed of two non-covalently associated transmembrane subunits: The Ī± and Ī² subunits combine to form a functional integrin receptor. Integrins are the major molecular bridges connecting the extracellular matrix to the intracellular cytoskeleton and signaling machinery. 2. Basic Structure A typical integrin spans the plasma membrane. 3. Integrin Heterodimers The functional receptor is an Ī±Ī² heterodimer. Different combinations of Ī± and Ī² subunits produce integrins with different ligandRead More →