Advanced Cell Biology. Lecture 33 Alexey Shipunov Minot State University April 22, 2013 Shipunov (MSU) Advanced Cell Biology. Lecture 33 April 22, 2013 1 / 38
Outline Questions and answers Intracellular transport Protein import Vesicular transport Transport in ER and AG Secretion and exocytosis Shipunov (MSU) Advanced Cell Biology. Lecture 33 April 22, 2013 2 / 38
Outline Questions and answers Intracellular transport Protein import Vesicular transport Transport in ER and AG Secretion and exocytosis Shipunov (MSU) Advanced Cell Biology. Lecture 33 April 22, 2013 2 / 38
Questions and answers Previous final question: the answer Why are neurotransmitters small molecules? Shipunov (MSU) Advanced Cell Biology. Lecture 33 April 22, 2013 3 / 38
Questions and answers Previous final question: the answer Why are neurotransmitters small molecules? To speed up and sharpen the process of transmission Shipunov (MSU) Advanced Cell Biology. Lecture 33 April 22, 2013 3 / 38
Protein import Intracellular transport Protein import Shipunov (MSU) Advanced Cell Biology. Lecture 33 April 22, 2013 4 / 38
Protein import Transport to ER Membrane-bound ribosomes form the rough ER (free ribosomes are in cytosol) If the protein contain SRP (signal-recognition particle), SRP receptor on ER membrane will bind ribosome New protein will move into ER lumen through translocation channel if it has one signal sequence Shipunov (MSU) Advanced Cell Biology. Lecture 33 April 22, 2013 5 / 38
Protein import ER tubules movie Shipunov (MSU) Advanced Cell Biology. Lecture 33 April 22, 2013 6 / 38
Protein import Shipunov (MSU) Advanced Cell Biology. Lecture 33 April 22, 2013 7 / 38
Protein import Shipunov (MSU) Advanced Cell Biology. Lecture 33 April 22, 2013 8 / 38
Protein import Transmembrane proteins Single-pass membrane proteins have start signal on the end and stop signal in the middle; they will stack halfway through the membrane Double pass membrane proteins have same signals both located inside molecule; they form U-shape because they double cross a membrane Shipunov (MSU) Advanced Cell Biology. Lecture 33 April 22, 2013 9 / 38
Protein import Protein translocation movie Shipunov (MSU) Advanced Cell Biology. Lecture 33 April 22, 2013 10 / 38
Protein import Shipunov (MSU) Advanced Cell Biology. Lecture 33 April 22, 2013 11 / 38
Protein import Shipunov (MSU) Advanced Cell Biology. Lecture 33 April 22, 2013 12 / 38
Vesicular transport Intracellular transport Vesicular transport Shipunov (MSU) Advanced Cell Biology. Lecture 33 April 22, 2013 13 / 38
Vesicular transport Vesicular transport Endocytic pathway: Plasma membrane endosome + vesicles lysosome Secretory pathway: ER AG transport vesicles plasma membrane Shipunov (MSU) Advanced Cell Biology. Lecture 33 April 22, 2013 14 / 38
Vesicular transport Moving cell compartments movie Shipunov (MSU) Advanced Cell Biology. Lecture 33 April 22, 2013 15 / 38
Vesicular transport Secretory pathway movie Shipunov (MSU) Advanced Cell Biology. Lecture 33 April 22, 2013 16 / 38
Vesicular transport Vesicle budding Starts with place covered with adaptin-clathrin complex Dynamin punch the vesicle Clathrin coat dissolved lately Shipunov (MSU) Advanced Cell Biology. Lecture 33 April 22, 2013 17 / 38
Vesicular transport Shipunov (MSU) Advanced Cell Biology. Lecture 33 April 22, 2013 18 / 38
Vesicular transport Clathrin movie Shipunov (MSU) Advanced Cell Biology. Lecture 33 April 22, 2013 19 / 38
Vesicular transport Shipunov (MSU) Advanced Cell Biology. Lecture 33 April 22, 2013 20 / 38
Vesicular transport Vesicle docking Rab and SNARE proteins allow recognition of different types of vesicles Rab-binding tethering proteins will lock vesicle nearby the membrane If SNAREs are complementary with SNAREs on target membrane, membranes will fuse Shipunov (MSU) Advanced Cell Biology. Lecture 33 April 22, 2013 21 / 38
Vesicular transport Shipunov (MSU) Advanced Cell Biology. Lecture 33 April 22, 2013 22 / 38
Vesicular transport Shipunov (MSU) Advanced Cell Biology. Lecture 33 April 22, 2013 23 / 38
Transport in ER and AG Intracellular transport Transport in ER and AG Shipunov (MSU) Advanced Cell Biology. Lecture 33 April 22, 2013 24 / 38
Transport in ER and AG Modification in ER Disulfide bonds Glycosilation through the dolichol N-linked oligosaccharide processing Shipunov (MSU) Advanced Cell Biology. Lecture 33 April 22, 2013 25 / 38
Transport in ER and AG Shipunov (MSU) Advanced Cell Biology. Lecture 33 April 22, 2013 26 / 38
Transport in ER and AG Exit from ER Proteins should have ER-retention signal Chaperones hold all misfolded proteins in ER (e.g., in case of cystic fibrosis) More misfolded proteins will activate unfolded protein response machinery and growth of ER itself Shipunov (MSU) Advanced Cell Biology. Lecture 33 April 22, 2013 27 / 38
Transport in ER and AG Shipunov (MSU) Advanced Cell Biology. Lecture 33 April 22, 2013 28 / 38
Transport in ER and AG Modification in AG AG has trans (exit) and cis (entry) faces Trans face sort proteins to lysosome and cell membrane proteins Further glycosilation happens inside AG Shipunov (MSU) Advanced Cell Biology. Lecture 33 April 22, 2013 29 / 38
Transport in ER and AG Shipunov (MSU) Advanced Cell Biology. Lecture 33 April 22, 2013 30 / 38
Secretion and exocytosis Intracellular transport Secretion and exocytosis Shipunov (MSU) Advanced Cell Biology. Lecture 33 April 22, 2013 31 / 38
Secretion and exocytosis Secretion and exocytosis Secterion starts from trans AG and ends in exocytosis to outer space Default secretion pathway is common to all cells Regulated pathway is specific to secretory cells (vesicles wait for releasing extracellular signal) Shipunov (MSU) Advanced Cell Biology. Lecture 33 April 22, 2013 32 / 38
Secretion and exocytosis Exocytosis movie Shipunov (MSU) Advanced Cell Biology. Lecture 33 April 22, 2013 33 / 38
Secretion and exocytosis Shipunov (MSU) Advanced Cell Biology. Lecture 33 April 22, 2013 34 / 38
Secretion and exocytosis Methods: protein labeling Radioactive and/or GFP labeling Temperature-sensitive mutants are used in order to freeze secretion at a given state Shipunov (MSU) Advanced Cell Biology. Lecture 33 April 22, 2013 35 / 38
Secretion and exocytosis Endocytosis and phagocytosis Endocytosis is a formation of endocytic vesicle Pinocytosis (cellular drinking ) take things normally < 150 nm in diameter Phagocytosis (cellular eating ) takes things which are generally > 250 nm Shipunov (MSU) Advanced Cell Biology. Lecture 33 April 22, 2013 36 / 38
Secretion and exocytosis Summary Moved protein bears signal sequence which corresponds with destination Protein coat is essential for vesicle budding and docking Proteins are undergoing serious modifications in ER lumen AG delivers excretion proteins to membrane Shipunov (MSU) Advanced Cell Biology. Lecture 33 April 22, 2013 37 / 38
Secretion and exocytosis For Further Reading A. Shipunov. Advanced Cell Biology [Electronic resource]. 2011 onwards. Mode of access: http://ashipunov.info/shipunov/school/biol_250 B. Alberts et al. Essential Cell Biology. 3rd edition. Garland Science, 2009. Chapter 15. Shipunov (MSU) Advanced Cell Biology. Lecture 33 April 22, 2013 38 / 38