Exam 4 Lesson 41 Flashcards Preview

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Flashcards in Exam 4 Lesson 41 Deck (46):
1

How is plant cell wall deposited?

in layers

2

what do successive layers of cellulose microfibrils reflect?

adjustments of microtubule orientation

3

layers of plant cell wall/membrane

plasma membrane, primary cell wall, middle lamella

4

components of primary cell wall

cross-linking glycan, cellulose microfibril, pectin

5

How are cellulose microfibrils aligned?

parallel to one another and perpendicular to the axis of cell elongation

6

how does expansion happen?

perpendicular to the orientation of the microfibrils, allowing cell to orient growth

7

In connective tissue in animals, when does orientation of secreted structural fibers like collage occur?

after secretion

8

What does orientation of cell fibers affect?

cell migration

9

what are fibroblasts?

the cells mainly responsible for secreting the ECM found in connective tissue

10

how can fibroblasts align collagen fibrils?

they can attach to and pull on a field of randomly oriented collagen fibrils to align them. Cells then move out along the collagen array. Tendons form by this mechanism in connective tissue.

11

Functions of the basal lamina

a. tissue stabilization
b. isolation of cells from other cells (bbb)
c. filtering of small molecules
d. signaling for cell proliferation, survival
e. determination of cell polarity

12

How is basal lamina structured?

it is a two-dimensional sheet of ECM made from specialized collagens and other glycoproteins and proteoglycans.

13

what are laminins?

they key organizing components of the basal lamina

14

how do cells bind to basal lamina?

via laminin receptors (integrins)

15

what does basal lamina mediate?

specialized interactions between cells, such as the neuromuscular junction

16

what controls how cells perceive and respond to signals?

the cell wall/ECM

17

what does the hydrated matrix control?

the "porosity" and physiochemical conditions in the ECM (controlling pore size, pH, ion concentrations, etc.)

18

What does controlling pore size do?

the matrix controls the ability of certain chemicals or growth factors to move through ECM.

19

What happens if a particular signal molecule can't pass through ECM?

the cell will not perceive the signal

20

How do signal molecules approach cell surface receptors?

Some signal molecules first bind to ECM components (like GAGs) and are then moved laterally to cell surface receptors. Others are only recognized by surface receptors if they are bound to one of the ECM components. In this case, the ECM component is a co-ligand or co-receptor.

21

What are integrins?

Type I membrane proteins with an N-terminal ectodomain domain and a C-terminal cytosolic domain.

22

What do integrins bind to?

an ECM component with their ectodomain and to anchor proteins with their cytosolic domain. The anchor protein s then link the integrins to the actin filaments.

23

how does fibronectin glycoprotein in ECM bind to certain integrins?

via an "RGD" motif

24

what is "integrin switching"?

an important part of EMT process and has major effects on properties like cell adhesion to the ECM and cell motility.

25

what is fibronectin?

a key organizer of the ECM
soluble proteins that form insoluble fibers on the cell surface when under tension (interactions with integrant). This is how cell controls organization of ECM supporting fibers.

26

what allows fibronectin to organize the ECM and bind to cells?

numerous protein-protein interaction domains

27

integrins can be "active" or "inactive" depending on

1. whether the ectodomains are bound to the ECM
2. whether the cytosolic domains are bound to the anchor proteins

28

How can integrins be activated to bind ECM and actin filaments?

by "outside-in" or "inside-out" signals

29

Outside-in activation

RGD peptide mimics the integrin binding site on fibronectin. In response to RGD, the conformation of the integrin ectodomain changes. The change is transmitted to the cytosolic domain, exposing a strong binding site for the anchor proteins and leading to an associating with actin filaments.

30

Inside-out activation of integrins

different signal transduction cascades can recruit talon (an anchor protein) to bind to beta integrin, leading to a conformational change in the ectodomain (activation) and binding to ECM components

31

what does actin cytoskeleton promote?

cell shape change, cell spreading, secretion of materials from storage granules

32

what can active integrins recruit?

protein kinases to assemble signaling scaffolds

33

Focal Adhesion Kinase (FAK)

tyrosine kinase phosphorylates itself and other target proteins at the anchor site, leading to inhibition/disassembly of focal adhesions

34

what can loss of FAK lead to?

too many focal adhesions, preventing cell spreading and inhibiting migration

35

what does elevated FAK contribute to?

overactive cell migration

36

what does integrin signaling depend on?

the types of integrins expressed by cell

37

What does integrin signaling cooperate with?

growth factor receptors

38

How does integrin signaling work?

through FAK kinase and Src family kinases (SFKs) to affect numerous signaling pathways

39

what does integrin signaling affect?

cell proliferation survival, migration

40

What kind of attachment do many cells require for survival? what can failure to attach lead to?

attachment to ECM/lamina
failure to attach can lead to
a. in early mouse embryo, endoderm cells send an apoptotic signal to ectoderm cells
b. ectoderm cells attached to basal lamina survive

41

what is "anchorage dependence"?

some cells require attachment to ECM molecules to survive/proliferate.

42

Do transformed cells/tumor cells have anchorage dependence?

no

43

How does FAK regulate cell proliferation?

it interacts with growth factor receptors to control the ERK/MAPK pathway

44

do animal stem cells need to be attached to lamina to survive?

yes

45

what do some cells do in order to migrate?

they secrete specific proteases that degrade proteins in the ECM. Examples are matrix metalloproteases or serene proteases.

46

How do cells secrete degrading proteases?

some cells secrete inactive proteases into the ECM and activate them with a second secreted activator in a local region.
other cells secrete inactive proteases into the ECM, then bind them to surface receptors at particular points on the cell surface.