kuliah_BiologiSel_Sitoskeleton2

FILAMEN MIKRO

form a band just beneath the plasma membrane that

provides mechanical strength to the cell

links transmembrane proteins (e.g., cell surface

receptors) to cytoplasmic proteins

anchors the centrosomes at opposite poles of the cell

during mitosis

pinches dividing animal cells apart during cytokinesis

generate cytoplasmic streaming in some cells

generate locomotion in cells such as white blood cells

and the amoeba

interact with myosin ("thick") filaments in skeletal muscle

fibers to provide the force of muscular contraction

Fungsi-fungsi filamen mikro

awalnya dianggap berfungsi pasif

Porter 1976: mf terlibat dalam sistem transpor sitoplasma

Studi lebih lanjut: terlibat dalam banyak hal yang

berkenaan dengan fungsi aktif (mis. aktin miosin otot)

Struktur 3D hanya bisa dilihat dalam sel utuh/sayatan

tebal, termasuk dalam sel-sel non-otot

sampai saat ini hanya diidentifikasi dalam sel-sel eukariot

berdasarkan ukurannya:

filamen aktin (cell contraction & movement)

filamen intermediet: neurofilamen, tonofilamen,

prekeratin-filamen, dll (regulate the cell shape?)

FILAMEN MIKRO

FILAMEN MIKRO

Komponen penyusun: protein aktin

G-aktin – globular actin: monomer

F-aktin – filament actin: polymer

FILAMEN MIKRO

+ protein asesoris beragam bentuk & fungsi:

muscle specific actin: α-actin

non-muscle actin:

β-actin: ujung-

ujung apikal sel

-actin: basal &

lateral sel

actin-related protein

(Arp): pembentukan

inti filamen,

terutama pada sel-

sel bermigrasi

FILAMEN MIKRO

+ actin-binding proteins: mengatur interaksi antar filamen,

misal: miosin II dalam struktur miofibril

FILAMEN MIKRO – decorating actin MF

MICROFILAMENT – micovillus structure

FILAMEN MIKRO – struktur 3 dimensi oleh dimer filamen

FILAMEN MIKRO – branched actin networks

frog keratocyte cell: deep

etch TEM

actin monomer was

fluorescently labelled

the antibody attached

to gold particles

FILAMEN MIKRO – branched actin networks

FILAMEN MIKRO

FILAMEN MIKRO: miofibril

myoblas sinsitium sel otot fungsional

dalam sel otot fungsional: bundel-bundel miofibril

satu bundel miofibril : filamen tipis (dominan aktin),

filamen tebal (dominan miosin) & berbagai protein

asesoris memunculkan pita-pita terang & gelap

FILAMEN MIKRO: miofibril

kontraksi otot

FILAMEN INTERMEDIET

ukuran 8-12 nm: antara tubulus mikro dan filamen mikro

deskripsi awal: antara aktin dan miosin

paling stabil dalam struktur polimer: that they serve as a

scaffold to support the entire cytoskeletal framework

mis.: neurofilamen, tonofilamen, prekeratin-filamen, dll

(regulate the cell shape?)

FILAMEN INTERMEDIET

(hanya) ditemukan pada organisme multisel

Protein fibrosa (bukan globular) dengan beragam

bentuk, struktur dan komponen penyusun:

I. Acidic cytokeratins – epitel

II. Basic cytokeratins - epitel

III. Vimentin – fiboblas, mesenkim, sel lensa mata

Desmin – otot (terutama otot polos)

GFA protein – sel-sel glial (terutama astrosit)

IV. Neurofilamen proteins – syaraf pusat dan tepi

V. Nuclear lamin – semua jenis sel multiselular

VI. Nestin – neuronal stem cells

IF typing serve as diagnostic tool, esp in metastasis stage of

cancer

FILAMEN INTERMEDIET

I II III IV V

FILAMEN INTERMEDIET

dimer tetramer protofilamen IF