Abstract
Although exosomes were first described in reticulocytes in 1983, many people do not realize that similar vesicles had been studied in the context of muscle and nerve, beginning in 1980. At the time of their discovery, these vesicles were named adherons, and they were found to play an important role in both cell–substrate and cell–cell adhesion. My laboratory described several molecules that are present in adherons, including heparan sulfate proteoglycans (HSPGs) and purpurin. HSPGs have since been shown to play a variety of key roles in brain physiology. Purpurin has a number of important functions in the retina, including a role in nerve cell differentiation and regeneration. In this review, I discuss the discovery of adherons and how that led to continuing studies on their role in the brain with a particular focus on HSPGs.
Highlights
All cells have, to varying extents, physical contact with the extracellular space surrounding them
The extracellular matrix (ECM) constitutes a significant part of its mass, but compared to other aspects of brain physiology, relatively little is known about its structure, assembly, and function
This material that we termed substrate-attached material (SAM) was clearly a subset of the total secreted material and appeared to be involved in promoting the adhesion of the cells to culture dishes [7]. Growth factors, such as nerve growth factor (NGF) and insulin, increased cell–substratum adhesion, in part, by modifying the composition of SAM [8]. This led to the question of what was the composition of SAM, which we considered an in vitro surrogate of ECM, and how was it delivered to the extracellular space?
Summary
To varying extents, physical contact with the extracellular space surrounding them. Because the use of cultured cells was an established paradigm in immunology, the approach of my lab in the new neuroscience department was to use cultured cells of both neuronal and non-neuronal origin to identify proteins involved in cellular differentiation and function. We both made and used myoblast cell lines from skeletal muscle to study synapse formation as well as the popular H9 cardiomyocyte cell line. This led to the question of what was the composition of SAM, which we considered an in vitro surrogate of ECM, and how was it delivered to the extracellular space?
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