Epidermal Barrier

Question 1

What is a cysteine-rich highly flexible protein with glycine loops that forms the major structural component of the cornified envelope?

Answer 1

loricrin

Question 2

What are the components of the lamellar granules/bodies?

Answer 2

extracellular lipids (phospholipids, glucosylceramides, spingomyelin, cholesterol), enzymes and their inhibitors (lipid hydrolases such as beta-glucocerebrosidase, acidic sphingomyelinase, secretory phospholipase A2, serine and cysteine proteases, kallikreins, cathepsins); corneodesmosin, steroid sulfatase, antimicrobial peptides (beta-defensin 2 and cathelicidin LL-37)

Question 3

What protease is required for filaggrin degradation?

Answer 3

capsase-14

Question 4

What are type II keratins?

Answer 4

basic to neutral, larger and include K1-8 in epidermis

Question 5

Where are functional tight junctions located in the epidermis?

Answer 5

stratum granulosum

Question 6

Epidermal tight junctions are composed of 2 families of transmembrane molecules. What are they?

Answer 6

claudins and occludins

Question 7

What do the corneodesmosomes contain?

Answer 7

desmoglein 1, desmocollin 1, corneodesmosin

Question 8

The epidermis can syntheize saturated and monounsaturated fatty acids but not what fatty acids?

Answer 8

omega-6 polyunsaturated essential fatty acids (EFAs) such as linoleic acid and alpha-linolenic acid

Question 9

What is a calcium dependent family of enzymes that catalyzes the formation of N(e)-(y-glutamyl)-lysine isopeptide bonds?

Answer 9

transglutaminases

Question 10

What proteins from the plakin protein family are present in the desmosomes?

Answer 10

desmoplakin, envoplakin, and periplakin

Question 11

Describe keratin intermediate filament assembly

Answer 11

type I and type II keratin molecules form coiled-coil heterodimers –> align in antiparallel and staggered pattern to form double coiled-coil tetramers –> assemble end-to-end to form protofilaments –> assemble laterally into protofibrils –> associate into intermediate filaments

Question 12

As the cornified envelope is formed, what proteins are expressed at the desmosomal plaques?

Answer 12

envoplakin and periplakin

Question 13

What are type I keratins?

Answer 13

acidic, smaller, K9-19 in epidermis

Question 14

What enzymes are involved in desquamation?

Answer 14

kallikreins and cathepsins

Question 15

What are the rate limiting enzymes in free fatty synthesis?

Answer 15

acetyl-CoA carboxylase and fatty acid synthase

Question 16

What is the primary signal for inducing lamellar granule secretion?

Answer 16

increase in extracellular calcium concentration in the granular layer

Question 17

Describe the calcium gradient in the layers of the epidermis

Answer 17

Ca2+ levels are low in the basal and spinous layers –> increase towards the stratum granulosum –> decrease in the stratum corneum

Question 18

What composes the corneocyte lipid envelope?

Answer 18

omega-hydroxyceramides

Question 19

What is the structure of keratin proteins?

Answer 19

central alpha-helical rod domain, amino-terminal head, carboxy-terminal tail

Question 20

T/F: Cholesterol must be obtained from the diet.

Answer 20

False - synthesized from acetate in the lower epidermis

Question 21

What is a highly soluble glutamine-rich protein that forms a scaffold for the attachment of other components of the cornified envelope (connects corneocytes to extracellular lipid layer)?

Answer 21

involucrin

Question 22

Where is profilaggrin cleaved into filaggrin (what cell layer)?

Answer 22

transition from granular to cornified layers

Question 23

What is the rate-limiting step in cholesterol synthesis?

Answer 23

hydroxymethylglutaryl CoA reductase

Question 24

What are adherens junctions?

Answer 24

cadherin-based junctions that link the actin cytoskeleton to the plasma membrane

Question 25

Desquamation involves enzymatic cleavage of what attachment between corneocytes?

Answer 25

corneodesmosomes

Question 26

What are the primary components of the keratohyalin granules?

Answer 26

profilaggrin, loricrin, keratin filaments

Question 27

What is the action of phospholipase in development of the cornified envelope?

Answer 27

cleaves phospholipids into free fatty acids and glycerol