Self-assembly of laminin isoforms.
The alpha, beta, and gamma subunits of basement membrane laminins can combine into different heterotrimeric molecules with either three full short arms (e.g. laminins-1-4), or molecules containing one (laminins-6-9) or more (laminin-5) short arm truncations. Laminin-1 (alpha1beta1gamma1), self-assembles through a calcium-dependent thermal gelation requiring binding interactions between N-terminal short arm domains, forming a meshwork polymer thought to contribute to basement membrane architecture (Yurchenco, P. D., and Cheng, Y. S. (1993) J. Biol. Chem. 268, 17286-17299). However, it has been unclear whether other isoforms share this property, and if so, which ones. To begin to address this, we evaluated laminin-2 (alpha2beta1gamma1), laminin-4 (alpha2beta2gamma1), laminin-5 (alpha3Abeta3gamma2), and laminin-6 (alpha3Abeta1gamma1). The first two isoforms were found to self-aggregate in a concentration- and temperature-dependent manner and a close self-assembly relationship among laminins-1, -2, and -4 were demonstrated by: (a) polymerization of all three proteins was inhibited by EDTA and laminin-1 short arm fragments, (b) polymerization of laminin-1 was inhibited by fragments of laminins-2 and -4, (c) laminin-2 and, to a lesser degree, laminin-4, even well below their own critical concentration, co-aggregated with laminin-1, evidence for co-polymerization. Laminin-5, on the other hand, neither polymerized nor co-polymerized with laminin-1. Laminin-6 failed to co-aggregate with laminin-1 at all concentrations evaluated, evidence for a lack of a related self-assembly activity. The data support the hypothesis that all three short arms are required for self-assembly and suggest that the short arm domain structure of laminin isoforms affect their architecture-forming properties in basement membranes.
Cheng
Y S
YS
Department of Pathology and Laboratory Medicine, Robert Wood Johnson Medical School, Piscataway, New Jersey 08854, USA.
Champliaud
M F
MF
Burgeson
R E
RE
Marinkovich
M P
MP
Yurchenco
P D
PD
D000818:Animals; D015815:Cell Adhesion Molecules / Q000737:chemistry; D004591:Electrophoresis, Polyacrylamide Gel; D007797:Laminin / Q000737:chemistry*; D051379:Mice; D008958:Models, Molecular; D010196:Pancreatic Elastase / Q000378:metabolism; D011108:Polymers / Q000378:metabolism; D011487:Protein Conformation; D014407:Tumor Cells, Cultured; D000097794:Kalinin
D015815:Cell Adhesion Molecules; D007797:Laminin; D010196:Pancreatic Elastase; D011108:Polymers; D000097794:Kalinin; C501370:Lama4 protein, mouse; C102645:laminin alpha 2; C095567:laminin alpha 3