Advanced Cell Biology. Lecture 38 Advanced Cell Biology. Lecture 38 Alexey Shipunov Minot State University April 30, 2012
Advanced Cell Biology. Lecture 38
Advanced Cell Biology. Lecture 38
Alexey Shipunov
Minot State University
April 30, 2012
Advanced Cell Biology. Lecture 38
Outline
Questions and answers
Cytoskeleton
Structure of cytoskeleton
Advanced Cell Biology. Lecture 38
Outline
Questions and answers
Cytoskeleton
Structure of cytoskeleton
Advanced Cell Biology. Lecture 38
Outline
Questions and answers
Cytoskeleton
Structure of cytoskeleton
Advanced Cell Biology. Lecture 38
Questions and answers
Previous final question: the answer
How do researchers use constantly active Ras protein?
I For determining sequence of proteins in a signal pathway
Advanced Cell Biology. Lecture 38
Questions and answers
Previous final question: the answer
How do researchers use constantly active Ras protein?
I For determining sequence of proteins in a signal pathway
Advanced Cell Biology. Lecture 38
Structure of cytoskeleton
Cytoskeleton
I Filament-like: intermediary filaments and actin filamentsI MicrotubulesI All are polymers of proteins
Advanced Cell Biology. Lecture 38
Structure of cytoskeleton
Intermediate filaments
I Keratin in epithelial cellsI Vimentin in connective-tissue cellsI NeurofilamentsI Nuclear laminsI Strengthening cell
Advanced Cell Biology. Lecture 38
Structure of cytoskeleton
Strengthening of cell layer
Advanced Cell Biology. Lecture 38
Structure of cytoskeleton
Microtubules
I Grow from centrosomeI Form flagella or ciliaI Form mitotic spindleI Organize interior of cellI Drive intracellular transport
Advanced Cell Biology. Lecture 38
Structure of cytoskeleton
Microtubules
Advanced Cell Biology. Lecture 38
Structure of cytoskeleton
Growth and shrinking of microtubules
I Microtubule is made of 13 tubulin microfilaments, eachcontain pairs of β-tubulin (– end) and α-tubulin (+ end)
I Tubulin dimers bind GTP and form a growing GTP cap ofmicrotubule; if GTP cap is lost, microtubules start to shrink
I Capturing the plus end will stabilize microtubule
Advanced Cell Biology. Lecture 38
Structure of cytoskeleton
Growing and shrinking of microtubules
Advanced Cell Biology. Lecture 38
Structure of cytoskeleton
Microtubule-specific drugs
Advanced Cell Biology. Lecture 38
Structure of cytoskeleton
Centrosomes
I γ-tubulin rings: starting places of microtubule growthI Two perpendicular centrioles (they are similar to basal
bodies of flagella)I Cetrosome has a fisherman-like behavior: microtubules
are constantly growing out of it, then degrading, but someare stabilizing
Advanced Cell Biology. Lecture 38
Structure of cytoskeleton
Motor proteins
I Kinesins and dyneins are dimers that hydrolyze ATP andmove
I They can move molecules and even whole organelles
Advanced Cell Biology. Lecture 38
Structure of cytoskeleton
Kinesin and dynein
Advanced Cell Biology. Lecture 38
Structure of cytoskeleton
Organelle movement movie
Advanced Cell Biology. Lecture 38
Structure of cytoskeleton
Flagella/cilia
I Hairlike structures growing from cytoplasmic basal bodiesI Contain 9×2 + 2 microtubules connected by dynein armsI They are natural oars
Advanced Cell Biology. Lecture 38
Structure of cytoskeleton
9 × 2 + 2 structure of flagella
Advanced Cell Biology. Lecture 38
Structure of cytoskeleton
Flagella bending
Advanced Cell Biology. Lecture 38
Structure of cytoskeleton
Actin filaments
I Fast-growing and unstable, they need to contact withmultiple protein types (e.g., capping proteins stabilize actinends)
I Actin filaments are polar, but thinner and shorter thanmicrotubules, ATP-binding
I Allow cell to change its form
Advanced Cell Biology. Lecture 38
Structure of cytoskeleton
Growing and shrinking of actin filaments
Advanced Cell Biology. Lecture 38
Structure of cytoskeleton
Actin binding proteins
Advanced Cell Biology. Lecture 38
Structure of cytoskeleton
Cell crawling
I Web of growing actin filament will push the leading edge ofpseudopodium forward
I ARPs are starting poins of new filaments, formins promotefilament growing
Advanced Cell Biology. Lecture 38
Structure of cytoskeleton
Formation of pseudopodium
Advanced Cell Biology. Lecture 38
Structure of cytoskeleton
Myosin
I Two subfamilies of ATP-binding motor proteinsI Myosin-I have one head and one tail, myosin-II (in muscle
cells) are two-headedI GTP-binding Rho proteins activate actin polymerization
and subsequently the movement of cell
Advanced Cell Biology. Lecture 38
Structure of cytoskeleton
Myosin-I
Advanced Cell Biology. Lecture 38
Structure of cytoskeleton
Myosin-II
Advanced Cell Biology. Lecture 38
Structure of cytoskeleton
Final question (1 point)
What will happen with cell if microtubuleswill not be able to grow?
Advanced Cell Biology. Lecture 38
Structure of cytoskeleton
Final question (1 point)
What will happen with cell if microtubuleswill not be able to grow?
Advanced Cell Biology. Lecture 38
Structure of cytoskeleton
Summary
I Intermediary filaments are polymers of ropelike polymersof fibrous proteins
I Microtubules are labile hollow tubes of tubulin, kinesinsand dyneins move along microtubules
I Actin filaments are helical polymers of actin; myosins movealong actin
Advanced Cell Biology. Lecture 38
Structure of cytoskeleton
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 17.