Proteolytic cleavage of the developmentally important cadherin BT-R1 in the midgut epithelium of Manduca sexta.
BT-R1 (M(r) = 210 kDa) represents a new type of insect cadherin that is expressed specifically in the midgut epithelium during growth and development of Manduca sexta larvae. It also is a target receptor for the Cry1A toxins of the entomopathogenic bacterium Bacillus thuringiensis. Expression of BT-R1, which varies during larval development, correlates with the abundance of the protein and with the differential cleavage of the molecule at each developmental stage. The cleavage of BT-R1 is calcium dependent, and consequently, Ca2+ directly influences the structural integrity of BT-R1. Indeed, removal of calcium ions by chelating agents promotes cleavage of the BT-R1 ectodomain, resulting in formation of fragments that are similar to those observed during larval development. Partial purification of proteins from brush border membrane vesicles (BBMVs) by gel filtration chromatography hinders the cleavage of BT-R1 in the presence of EDTA and EGTA, indicating that there is specific proteolytic activity associated with the BBMV. This specific proteolytic cleavage of BT-R1 not only alters the integrity of BT-R1 but it most likely is implicated in cell adhesion events during differentiation and development of M. sexta midgut epithelium. We propose a model for calcium-dependent protection of BT-R1 as well as a cleavage pattern that may modulate the molecular interactions and adhesive properties of its ectodomain. Molecular characterization of such a protection mechanism should lead to a better understanding of how the function of specific cadherins is modulated during tissue differentiation and insect development.
Candas
Mehmet
M
Center for Biotechnology and Bioinformatics and Department of Molecular and Cell Biology, The University of Texas at Dallas, Richardson, Texas 75083, USA.
Francis
Brian R
BR
Griko
Natalya B
NB
Midboe
Eric G
EG
Bulla
Lee A
LA
D000818:Animals; D001413:Bacillus thuringiensis; D001426:Bacterial Proteins; D015820:Cadherins / Q000737:chemistry*; D002460:Cell Line; D002942:Circular Dichroism; D003001:Cloning, Molecular; D004064:Digestive System / Q000378:metabolism*; D004731:Endotoxins / Q000378:metabolism; D004848:Epithelium / Q000378:metabolism*; D019476:Insect Proteins; D007814:Larva / Q000254:growth & development / Q000378:metabolism; D018402:Manduca / Q000254:growth & development / Q000378:metabolism*; D008871:Microvilli; D008954:Models, Biological; D010446:Peptide Fragments / Q000737:chemistry / Q000235:genetics / Q000302:isolation & purification / Q000378:metabolism*; D011480:Protease Inhibitors / Q000494:pharmacology*; D011956:Receptors, Cell Surface / Q000378:metabolism*; D011994:Recombinant Proteins / Q000737:chemistry / Q000378:metabolism
D001426:Bacterial Proteins; D015820:Cadherins; C095416:Cry toxin receptors; D004731:Endotoxins; D019476:Insect Proteins; D010446:Peptide Fragments; D011480:Protease Inhibitors; D011956:Receptors, Cell Surface; D011994:Recombinant Proteins