1.13 ECM I - GAG's and Proteoglycans Flashcards
The ECM is composed of what three things?
Water
Proteins
Polysaccharides
What is the Extracellular Matrix?
Non Cellular component within all tissues and organs.
What is major component of ECM
Water
What are the three classes of molecules found in the Extracellular Matrix
Glycoproteins
Glycosaminoglycans (GAGs)
Proteoglycans
What is the ground substance?
The space between the cells and fibers
What is a Glycosaminoglycan (GAG)?
unbranched repeating disaccharides containing an amino sugar
List the four classes of glycoaminoglycans
Hyaluronan
Keratan Sulfate
Chondroiton Sulfate
Heparan Sulfate
Which of the GAGs does not carry a Sulfate
Hyaluronan
What causes GAGs to bring water into the matrix?
High density negative charges attract sodium and bring water into matrix
What is the chief function of GAGs
To maintain proper homeostatic environment for cells and fibrous elements
What is a Proteoglycan?
One or more GAGs are COVALENTLY joined to a membrane or secreted protein
T or F, Hyaluronic Acid does not form Proteoglycans?
True
What are the three classes of Proteoglycans?
Small Leucine-Rich Proteoglycans (SLRPs)
Modular Proteoglycans
Cell Surface Proteoglycans
What is the major structural proteoglycan found in cartliage?
Aggrecan
T or F, Proteoglycans directly bind to hyaluronan forming giant proteoglycan aggregates
False, They INDIRECTLY bind to Hyaluronan through linker proteins
What is a function of Syndecan-1, a proteoglycan?
Binds Chemokines which play a role in inflammation
GAGs are covalently linked to the protein core in Proteoglycans. Explain this linkage further
The GAGs are attached via a Serine residue in the core protein.
Compare Normal PG catabolism and Abnormal PG catabolism
Normal: Bone replacing cartilage during development
Abnormal: Tumor invasions, arthritis
How are Proteoglycans mostly degraded?
Through lysosomes
What happens when GAGs can’t be broken down?
It is a lysosomal storage disease
What two GAGs do not accumulate due to the lysosomal storage deficiency?
Hyaluronate and Chondroiton sulfate because they can be catabolized through other pathways
