Laminins are a family of multifunctional macromolecules,
ubiquitous in basement membranes, and represent
the most abundant structural noncollagenous glycoproteins of these
highly specialised extracellular matrices.
Their discovery started with the difficult task of isolating
molecules produced by cultivated cells or extracted
from tissues. The development of molecular biology techniques
has facilitated and accelerated the
identification and the characterisation of new laminin variants
making it feasible to identify full-length
polypeptides which have not been purified. Further, genetically
engineered laminin fragments can be
generated for studies of their structure-function relationship,
permitting the demonstration that laminins are
involved in multiple interactions with themselves, with other
components of the basal lamina, and with cells.
It endows laminins with a central role in the formation, the
architecture, and the stability of basement
membranes. In addition, laminins may both separate and connect
different tissues, i.e. the parenchymal and
the interstitial connective tissues. Laminins also provide
adjacent cells with a mechanical scaffold and
biological information either directly by interacting with
cell surface components, or indirectly by trapping
growth factors. In doing so they trigger and control cellular
functions. Recently, the structural and
biological diversity of the laminins has started to be elucidated
by gene targeting and by the identification of
laminin defects in acquired or inherited human diseases. The
consequent phenotypes highlight the pivotal
role of laminins in determining heterogeneity in basement membrane functions.