Laminin aggregation

In summary, both collagen IV and laminin show the ability to self-assemble. In addition, the various components of basement membrane have an affinity for one another that involves binding to specific sites. These interactions generate rather defined aggregates in solution and lead to the deposition of the components in a gel-like form whose ultrastructure resembles in some details authentic basement membranes. Such multiple interactions would be expected to be stronger than single interactions and may account for the codistributions of these components in basement membranes. 

When plated onto untreated dished F9 cells proliferate rapidly and form clumps of necrotic spheres by 4-8 days. In the presence of 5x10-8M retinoic acid (supplied from a stock of 1 mg/ml in DMSO) proliferation and aggregation occurs but, by about 5 days, embryoid bodies are formed which remain stable for more than 25 days (Adamson and Grover, 1983). It is in the early stages that differentiated functions are first expressed and alpha foetoprotein can be detected in the outer cells of the embryoid bodies at 6-8 days depending on the initial seeding density. There is increased production of laminin at 2 days. 

Fig. 3. Model of the life cycle of prions. PrP is synthesized in the rough endoplas-matic reticulum (ER), and after passing through the secretory pathway including the Golgi and secretory vesicles, reaches the surface of a PrP infectable cell where it is anchored via a glycosylphosphatidyl inositol (GPI) moiety. Endocytosis of PrP and possibly PrP via clathrin coated vesicles could be mediated by the 37 kDa laminin receptor precursor (LRP). The uptake of the infectious agent could also be LRP independent. The conversion of the internalized PrP to PrP is thought to take place in the endo-somes, lysosomes, or endolysosomes. Molecular chaperones could be involved in this conversion process. PrP replication and aggregation can occur in neuronal cells of the brain but also in the cells constituting the lymphoreticular system. Alternatively, endocytosis and conversion of PrP into PrP could happen in caveolae-like domains (CLDs).

Laminin itself will aggregate in vitro into large polymers in a temperature-, time- and concentration-dependent manner. Aggregation exhibits both concentration and thermal reversibility and there is a critical concentration for polymerization of about 60 nM, reflecting cooperative nucleation-propaga-tion type assembly (Yurchenco et al., 1985). Diva-... 

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