The enzyme cleaves another key component of BM and ECM, namely heparan sulphate proteoglycans (HSPG) which belong to the glycosaminoglycans.
Smetana et al. [ 28] reported that laminins, a principal component of BM, exhibit unique saccharidic epitopes (mannose-rich oligosaccharides).
Laminin-1 is a heterotrimer of α1, β1 and γ1 chains, and is a major component of BM (for review [ 24]).
MMP-9, also known as gelatinase B, is able to degrade collagens IV (the main component of BM) and V, gelatins, and elastin.
It is caused by defects of type IV collagen, which is the major structural component of BM and necessary for BM maintenance [ 1].
The extracellular matrix HS proteoglycans collagen type XVIII (collXVIII), perlecan and agrin are components of BMs of various tissues [9] [11].
Yamazaki et al. reported that TGF-β produced by glial cells (one of the components of BM niche) was critical for the maintenance of BM niche [ 52].
As type IV collagen is one of the integral components of BM, the uncontrolled expression of two type IV collagenases, MMP-9, is believed to play a critical role in the invasion of BM by tumor cells [ 20].
Since defects in the structural components of BM, that is, respective laminins and collagen IV, are not compatible with early embryonic development, we like to focus here mainly on deletions or functional defaults of the bridging molecules nidogen and perlecan.
We next tested whether the expression of GADD153 [32], [32] and the levels of laminin-5, a component of the BM of the mammary acinus [44] were affected by PERK inhibition.
