more obscure proteins and agents we need to know.

Filamin

Cross links microfilaments into a gel like network. (Fillament-crosslinking protein)

Villin

Villin bundles actin in microvilli. (Filament-bundling protein)

Fimbrin

Bundles actin filaments in parallel arrays. (Filament-bundling protein)

Alpha actinin

Links actin filaments into parallel arrays at the z-line in sarcomeres. (Filament bundling protein)

Spectrin

Forms a network under plasma membrane providing support. Helps other proteins bind to membrane (E.g dynactin complex will bind to membrane associated spectrin during power stroke step of calcium cycle).

Takin

Links actin filaments to integrins at focal adhesions. Binds to vinculin and alpha actinin which can bind directly to actin MFs.

Dystrophin

Large protein found at muscle costameres that is part of a complex of proteins that attaches the muscle cell plasma membrane to the extracellular matrix. “Links actin cytoskeleton to ECM in muscle cells”

Thymosin B 4

Sequesters actin monomers, preventing polymerization in MFs. (Monomer-sequestering protein)

Profilin

Appears to compete with Thyomisin beta 4 for binding to G-actin monomers. “Facilitates actin polymerization by promoting ATP change.” (Monomer-polymerizing proteins)

Cofilin

“Cofilin severs filaments, creating new plus and minus ends.” “Severs actin filaments and promotes turnover”

Gelsolin

“Functions by breaking actin MFs and capping their newly exposed plus ends, thereby preventing further polymerization.” (Labeled as Filament-Severing protein though)

Formin

Nucleate linear actin filament growth (Actin-polymerizing proteins).

Capz

Caps MF at barbed end (plus end) to regulate growth of MFs. (Filament-capping proteins)

Cortactin

Stabilizes branched actin networks. Not even in the book idk man…

Tropomodulin

Caps pointed ends (minus end) of F-actin.

Arp2/3 complex

Complex of actin-related proteins that allow the actin monomers to polymerize as new “branches” on the sides of existing MFs. Facilitates nucleation of MFs.

Types of actin binding proteins (and some examples)

Monomer sequestering proteins (thymosin beta 4), Actin-polymerizing proteins (formin), Filament- severing proteins (gelsolin), Filament -capping proteins (capz), filament-crosslinking proteins (filamin), filament-bundling proteins (alpha actinin and fimbrin)

Colchicine/ colcemid

Binds to beta tubulin, inhibits assembly

Nocadazole

Binds beta tubulin, inhibits polymerization.

Vinblastine/ vincristine

Aggregates tubulin heterodimers

Paclitaxel (Taxol)

Stabilizes microtubules

Agents affecting microtubules (that he told us to memorize)

Colchicine/ colcemid, Nocadazole, Vinblastine/ vincristine, paclitaxel (Taxol).

Agents affecting Microfilaments (that we need to know)

Cytochalasin D, Latrunculin A, Phalloidin.

Agents affecting IFs (hint only one)

Acrylamide, causes loss of intermediate filament networks.

Cytochalasin D

Prevents addition of new monomers to plus ends of Mfs

Latrunculin A

Sequesters actin monomers in Mfs

Phalloidin

Binds and stabilizes assembled Mfs

Rac

Member of a family of Rho GTPases (monomeric G proteins that are localized to the plasma membrane where a lipid modification keeps them attached to the inner leaflet of the plasma membrane). Rac stimulates formation of various actin-containing structures within cells. Active when bound to GTP

Cdc42

Part of the Rho GTPases (monomeric G proteins that are localized to plasma membrane through a lipid modification that keeps them attached to the inner leaflet of the plasma membrane). Stimulates formation of various actin-containing structures. Active when bound to GTP

Rho GTPases

Family of monomeric G proteins, which include Rho Rac and Cdc42, that stimulate formation of various actin-containing structures within cells. They give rise to the dramatic change seen in the cytoskeleton when exposed to growth factors.

Inositol phospholipids

Inositol phospholipids are a type of membrane phospholipid that regulates actin assembly. One species PIP2 can bind to profilin, Capz and recruit them to the plasma membrane.