Thrombomodulin-mediated cell adhesion: involvement of its lectin-like domain.
Thrombomodulin (TM) is an integral membrane glycoprotein that is a potent anticoagulant factor. TM may also possess functions distinct from its anticoagulant activity. Here the influence of TM on cell adhesion was studied in TM-negative melanoma A2058 cells transfected with green fluorescent protein-tagged TM (TMG) or lectin domain-deleted TM (TMG(DeltaL)). Confocal microscopy demonstrated that both TMG and TMG(DeltaL) were distributed in the plasma membrane. TMG-expressed cells grew as closely clustered colonies, with TM localized prominently in the intercellular boundaries. TMG(DeltaL)-expressed cells grew singly. Overexpression of TMG, but not TMG(DeltaL), decreased monolayer permeability in vitro and tumor growth in vivo. The cell-to-cell adhesion in TMG-expressed cells was Ca2+-dependent and was inhibited by monoclonal antibody against the lectin-like domain of TM. The effects of TM-mediated cell adhesion were abolished by the addition of mannose, chondroitin sulfate A, or chondroitin sulfate C. In addition, anti-lectin-like domain antibody disrupted the close clustering of the endogenous TM-expressed keratinocyte HaCaT cell line derived from normal human epidermis. Double-labeling immunofluorescence staining revealed similar distributions of TM and actin filament in the cortex region of the TMG-expressed cells. Thus, TM can function as a Ca2+-dependent cell-to-cell adhesion molecule. Binding of specific carbohydrates to the lectin-like domain is essential for this specific function.
Huang
Huey-Chun
HC
Department of Biochemistry, College of Medicine, National Cheng Kung University, Tainan, Taiwan 701, Republic of China.
Shi
Guey-Yueh
GY
Jiang
Shinn-Jong
SJ
Shi
Chung-Sheng
CS
Wu
Chun-Mei
CM
Yang
Hsi-Yuan
HY
Wu
Hua-Lin
HL
D002118:Calcium / Q000494:pharmacology; D002448:Cell Adhesion; D045744:Cell Line, Tumor; D002462:Cell Membrane / Q000378:metabolism; D002809:Chondroitin Sulfates / Q000494:pharmacology; D006801:Humans; D037102:Lectins / Q000378:metabolism*; D008358:Mannose / Q000494:pharmacology; D018613:Microscopy, Confocal; D017434:Protein Structure, Tertiary; D017384:Sequence Deletion; D018180:Thrombomodulin / Q000737:chemistry / Q000235:genetics / Q000502:physiology*; D014162:Transfection
D037102:Lectins; D018180:Thrombomodulin; D002809:Chondroitin Sulfates; D008358:Mannose; D002118:Calcium