BIO230 Lecture 1: Cell, Tissue, and Organisms Membrane Trafficking Fall 2024 PDF

BIO230 Section 2: Cells, Tissues, and Organisms Lecture 1: Membrane Trafficking Fall 2024 BIO230 Section 2 – Lecture 1: Membrane Trafficking p. 749-750 Chapter 13 Overview: Intracellular Membrane Traffic p. 751-763 Mechanisms...

BIO230 Section 2: Cells, Tissues, and Organisms Lecture 1: Membrane Trafficking Fall 2024 BIO230 Section 2 – Lecture 1: Membrane Trafficking p. 749-750 Chapter 13 Overview: Intracellular Membrane Traffic p. 751-763 Mechanisms of Membrane Transport and Readings Compartment Identity (Alberts et al.) p. 776-777 all listed on Transport from the Trans Golgi Network to p. 780-781 Quercus the Cell Exterior and Endosomes p. 785-787 p. 788 Transport Into the Cell From the Plasma p. 791-798 Membrane: Endocytosis BIO230 Lecture 2-1 2 Section 2 Overview Bio230: From Genes to Organisms Section 1: Section 2: Genes to Cells Cells to Organisms BIO230 Lecture 2-1 3 Section 2: Big Biological Questions How do changes in gene expression lead to development? Cell types Tissues Organs Organisms How do cells change during development? Numbers Shapes Functions Interactions BIO230 Lecture 2-1 4 Section 2: Big Biological Questions What happens if organisms lose control of interactions, shapes, cell numbers, and/or functions? BIO230 Lecture 2-1 5 Section 2 Overview Lectures: 1-3: How are cells and tissues organized spatially? 4-6: How do multicellular organisms develop? 7-9: How do cells communicate with each other? 10-12: How are cell numbers controlled? BIO230 Lecture 2-1 6 Section 2 Overview: Lectures 1-3 Lectures 1-3: How are cells and tissues organized spatially? 1: Membrane Trafficking 2: Cytoskeletal Networks 3: Cell Adhesion BIO230 Lecture 2-1 7 Cell polarization is essential for multicellular organisms Polar = different at either end Apical domain Basolateral domain Polarized cells can: Have different functions at different cell regions Define inside vs outside Transmit signals from one end to the other BIO230 Lecture 2-1 8 Membrane trafficking can send different proteins to different domains 2. Exocytosis to any domain then 1. Exocytosis endocytosis directly to the followed by target domain recycling to the target domain BIO230 Lecture 2-1 9 Membrane trafficking determines where proteins end up Some trafficking routes are polarized Proteins are organized at sorting stations Different routes are balanced by retrieval pathways BIO230 Lecture 2-1 10 Key concepts in the secretory pathway Some trafficking routes are polarized (ER->Golgi->plasma membrane) Proteins are organized at sorting stations (trans-Golgi Network) Different routes are balanced by retrieval pathways (ER retrieval from Golgi) BIO230 Lecture 2-1 11 Constitutive secretion is the “default pathway” Most cargo moves through constitutive secretion Specific signals do not seem to be required for constitutive secretion BIO230 Lecture 2-1 12 Secretion can release concentrated cargo Clathrin-coated vesicles can return membrane back to the Golgi This shrinks the vesicle and makes the cargo more concentrated BIO230 Lecture 2-1 13 Regulated secretion can release material in response to a signal Regulated secretion vesicles are fully- formed but do not fuse with the plasma membrane until a signal is received e.g. Mast cell releasing stored histamine BIO230 Lecture 2-1 14 Regulated secretion can deliver extra membrane material BIO230 Lecture 2-1 15 Endocytosis can determine where proteins end up 2. Exocytosis to any domain then 1. Exocytosis endocytosis directly to the followed by target domain recycling to the target domain BIO230 Lecture 2-1 16 Proteins are removed from the plasma membrane via endocytosis Some trafficking routes are polarized (plasma membrane-> early endosome-> lysosome) Proteins are organized at sorting stations (endosomes) Different routes are balanced by retrieval pathways (re-secretion to plasma membrane) BIO230 Lecture 2-1 17 Endocytosed proteins have 3 options 1. Recycling to the same domain of the plasma membrane 2. Transcytosis to the other domain of the plasma membrane 3. Degradation in the lysosome BIO230 Lecture 2-1 18 Cholesterol uptake as an example of endocytosis BIO230 Lecture 2-1 19  Three types of membrane changes during vesicle trafficking 1. Vesicle forms from the donor membrane into the cytoplasm 2. Vesicle fusion: vesicle merges with a target membrane 3. Vesicle forms from a donor membrane away from the cytoplasm CYTOSOL BIO230 Lecture 2-1 20 Clathrin can mediate vesicle formation into the cytoplasm BIO230 Lecture 2-1 21 Vesicles coats are selective of cargo and specifically targeted BIO230 Lecture 2-1 22  SNARE proteins help to mediate vesicle fusion Both t-SNAREs & v- SNAREs are required t-SNARES and v-SNARES must be on opposite membranes BIO230 Lecture 2-1 23  ESCRT proteins can form vesicles away from the cytoplasm CYTOSOL Vesicles can form away from the cytoplasm (into lumen or extracellular space) Vesicle formation machinery is in the cytoplasm BIO230 Lecture 2-1 24 ESCRT proteins can form vesicles away from the cytoplasm BIO230 Lecture 2-1 25 Practice Exam Question 1 How many of the following are examples of vesicle formation into the cytoplasm? COPII-mediated secretory vesicle formation at the ER ESCRT-mediated vesicle formation clathrin-mediated endocytic vesicle formation any process mediated by SNARE proteins a) 0 b) 1 c) 2 d) 3 BIO230 Lecture 2-1 26 Phosphoinositides “label” different membrane domains Different membrane domains and compartments contain different lipids Different types of phosphoinositides (PIPs) are found at different subcellular locations BIO230 Lecture 2-1 27 All phosphoinositides (PIPs) share the same basic structure inositol sugar head group phosphate group glycerol glycerophospholipid lipids BIO230 Lecture 2-1 28 Phosphoinositides can be phosphorylated on the inositol sugar possible phosphorylation sites structural phosphate BIO230 Lecture 2-1 29 Phosphoinositides are named by their phosphorylated groups phosphorylation site positions total number of phosphorylation sites BIO230 Lecture 2-1 30 Phosphoinositides are interconverted by kinases & phosphatases PIP kinase PIP phosphatase BIO230 Lecture 2-1 31 Different proteins bind to different PIPs PIP(4,5)P2 PIP(3)P BIO230 Lecture 2-1 32 PI(4,5)P2 targets clathrin coat assembly BIO230 Lecture 2-1 33 Adaptor proteins bind PI(4,5)P2, cargo, and clathrin BIO230 Lecture 2-1 34 Rab GTPases are molecular switches that can direct vesicles Rab GTPases can act like molecular switches GEF exchanges GDP for GTP GAP activates GTPase BIO230 Lecture 2-1 35 Rabs and PIPs combine to give membranes different identities 1. Rab5-GTP recruits PI 3-kinse Example: early endosome 2. PI(3)P can recruit Rab5-GEF 3. More Rab5-GEF makes more active Rab5-GTP BIO230 Lecture 2-1 36 Rabs and SNAREs work together in vesicle targeting & fusion BIO230 Lecture 2-1 37 Both exocytosis and endocytosis can contribute to cell polarity 2. Exocytosis to any domain then 1. Exocytosis endocytosis directly to the followed by target domain recycling to the target domain BIO230 Lecture 2-1 38 Review the textbook and add to your notes. If that was too quick for you, or if you have additional questions, please review the textbook, review the recording (if available), post on the Discussion Board, stay for the Q&A sessions, and try ChatBIO230. This is your responsibility.