Primary Structure of the Drosophila Laminin B2 Chain and Comparison with Human, Mouse, and Drosophila Laminin B1 and B2 Chains

117

122

We report the molecular and functional characterization of a new α chain of laminin in Drosophila. The new laminin chain appears to be the Drosophila counterpart of both vertebrate α2 (also called merosin) and α1 chains, with a slightly higher degree of homology to α2, suggesting that this chain is an ancestral version of both α1 and α2 chains. During embryogenesis, the protein is associated with basement membranes of the digestive system and muscle attachment sites, and during larval stage it is found in a specific pattern in wing and eye discs. The gene is assigned to a locus called wing blister (wb), which is essential for embryonic viability. Embryonic phenotypes include twisted germbands and fewer pericardial cells, resulting in gaps in the presumptive heart and tracheal trunks, and myotubes detached from their target muscle attachment sites. Most phenotypes are in common with those observed in Drosophila laminin α3, 5 mutant embryos and many are in common with those observed in integrin mutations. Adult phenotypes show blisters in the wings in viable allelic combinations, similar to phenotypes observed in integrin genes. Mutation analysis in the eye demonstrates a function in rhabdomere organization. In summary, this new laminin α chain is essential for embryonic viability and is involved in processes requiring cell migration and cell adhesion.

mentioning

confidence: 99%

wing blister, A New Drosophila Laminin α Chain Required for Cell Adhesion and Migration during Embryonic and Imaginal Development

Martin

Zusman

et al. 1999

117

122

“…The complete amino acid sequence of the human, mouse and Drosophila A, B1, and B2 chains (Sasaki et al, , 1988Pikkarainen et al, 1987Pikkarainen et al, , 1988Montell et al, 1988Montell et al, , 1989Chi and Hui, 1989;Haaparanta et al, 1991;Nissinen et al, 1991;Kusche-Gullberg et al, 1992), the rat S chain (Hunter et al, 1989) and the human B2t chain has been determined. All the laminin chains have a characteristic structure with distinct domains containing cysteine-rich repeats, globular regions and helical structures.…”

mentioning

confidence: 99%

Human laminin M chain (merosin): complete primary structure, chromosomal assignment, and expression of the M and A chain in human fetal tissues

Vuolteenaho

Nissinen

Sainio

et al. 1994

244

104

Abstract. The primary structure of the human laminin M chain was determined from cDNA clones isolated from human placental libraries. The clones covered a total of 6,942 bp, with 49-bp encoding a 5' end untranslated region and 6,893-bp coding for a translated sequence. The complete human laminin M chain contains a 22-residue signal peptide and 3,088 residues of the mature M chain. The M chain has a domain structure similar to that of the human and mouse A chains.

“…Laminin, first isolated from a murine Engelbreth-Holm-Swarm (EHS) t tumor (70), was shown to be a heterotrimer consisting of one heavy A chain of 400 kD and two light chains, B1 and B2, of ,,o 200 kD each (14). The primary structure of the laminin A, B1, and B2 chains has been determined from mouse (1, 60, 61, 62), man (31, 51, 53, 54), and Drosophila (12,26,48,49). The laminin chains have a characteristic domain structure with internal repeats (2, 3).…”

mentioning

confidence: 99%

A truncated laminin chain homologous to the B2 chain: structure, spatial expression, and chromosomal assignment.

Kallunki

Sainio

Eddy

et al. 1992

214

118

Abstract. We describe the identification of a novel laminin chain. Overlapping clones were isolated from a human fibrosarcoma HTI080 cell cDNA library spanning a total of 5,200 bp. A second set of clones contained an alternative 3' end sequence giving a total of 4,316 bp. The longer sequence contained an open reading frame for a 1,193-residue-long polypeptide. The alternative sequence was shortened at the carboxylterminal end coding for a 1,111-residue-long polypeptide. The amino acid sequence contained 21 amino acids of a putative signal peptide and 1,172 residues or alternatively 1,090 residues of a sequence with five distinct domains homologous to domains I-V in laminin chains. Comparison of the amino acid sequences showed that the novel laminin chain is homologous to the laminin B2 chain. However, the structure of the novel laminin chain isolated here differs significantly from that of the B2 chain in that it has no domain VI and domains V, IV, and III are shorter, resulting in a truncated laminin chain. The alternative sequence had a shortened domain I/II. In accordance with the current nomenclature, the chain characterized here is termed B2t. Calculation of possible chain interactions of laminin chains with the B2t chain domain I/II indicated that the B2t chain can replace the B2 chain in some laminin molecules. The gene for the laminin B2t chain (LAMB2T) was localized to chromosome lq25-q31 in close proximity to the laminin B2 chain gene. Northern analysis showed that the B2t chain is expressed in several human fetal tissues but differently from the laminin B1 and B2 chains. By in situ hybridization expression of the B2t chain was localized to specific epithelial cells in skin, lung, and kidney as opposed to a general epithelial and endothelial cell expression of the laminin B2 chain in the same tissues.AMININS are large, basement membrane glycoproteins consisting of three chains connected by an u-helical coiled-coil domain. The laminin molecule has a crosslike structure with one long arm and three short arms (69). Laminin, first isolated from a murine Engelbreth-HolmSwarm (EHS) t tumor (70), was shown to be a heterotrimer consisting of one heavy A chain of 400 kD and two light chains, B1 and B2, of ,,o 200 kD each (14). The primary structure of the laminin A, B1, and B2 chains has been determined from mouse (1, 60, 61, 62), man (31,51,53,54), and Drosophila (12,26,48,49). The laminin chains have a characteristic domain structure with internal repeats (2, 3). The short arms are formed of EGF-like modules and globular domains. The long arm is formed by heptad repeats typical for a-helical coiled-coil proteins. Diverse biological functions attributed to laminin include stimulation of cell growth and differentiation, and promotion of neurite outgrowth, cell 1. Abbreviations used in this paper: EHS, Engelbreth-Holm-Swarm; HSPG, heparan sulfate proteoglycan. adhesion, and locomotion. The laminin molecule participates in the assembly of basement membranes through binding to other laminin molecules, type IV coll...