title: Localization of laminin-5 in the epidermal basement membrane.
abstract: Laminin-5 (kalinin/nicein/BM600) is a component of the epidermal basement membrane zone. Previous en bloc pre-embedding immunogold electron microscopy (EM) has shown that the epitope of GB3, a monoclonal antibody against laminin-5, is present in the lamina lucida (LL). However, precise localization of the entire laminin-5 molecule was unclear because of uneven and limited penetration of gold-labeled antibody in pre-embedding immunolabeling. In addition, the location of the GB3 epitope may not directly represent the location of the laminin-5 moelcule itself. To elucidate the precise ultrastructural distribution of the entire laminin-5 molecule, we used polyclonal antibodies against different sites of laminin-5. Dual staining immunofluorescence with anti-laminin-5 and anti-melanocyte antibodies and immunoperoxidase EM showed that laminin-5 was present only beneath keratinocytes and not beneath melanocytes. Both cryoultramicrotomy and postembedding immunogold EM demonstrated that laminin-5 was localized to the lamina densa (LD) and the lower LL, with major labeling beneath the hemidesmosome. Quantitative analysis showed that 67-69% of gold particles were distributed to the LD and 88-90% were distributed beneath the hemidesmosome. Our results indicate that laminin-5 is localized mainly to the LD and partially to the lower LL, and is associated predominantly with hemidesmosomes.
authors.affiliation: Department of Dermatology, Keio University School of Medicine, Tokyo, Japan.
authors.forename: T
authors.initials: T
authors.lastname: Masunaga
authors.forename: H
authors.initials: H
authors.lastname: Shimizu
authors.forename: A
authors.initials: A
authors.lastname: Ishiko
authors.forename: Y
authors.initials: Y
authors.lastname: Tomita
authors.forename: D
authors.initials: D
authors.lastname: Aberdam
authors.forename: J P
authors.initials: JP
authors.lastname: Ortonne
authors.forename: T
authors.initials: T
authors.lastname: Nishikawa
mesh_terms: D001485:Basement Membrane / Q000378:metabolism* / Q000648:ultrastructure; D015815:Cell Adhesion Molecules / Q000032:analysis*; D006801:Humans; D007150:Immunohistochemistry; D016253:Microscopy, Immunoelectron; D012867:Skin / Q000378:metabolism* / Q000648:ultrastructure; D000097794:Kalinin
chemical_list: D015815:Cell Adhesion Molecules; D000097794:Kalinin