A possible role for ligatin and the phosphoglycoproteins it binds in calcium-dependent retinal cell adhesion.
Ligatin is a filamentous plasma membrane protein that serves as a baseplate for the attachment of peripheral glycoproteins to the external cell surface. Ligatin can be released from intact, embryonic chick neural retinal cells by treatment with 20 mM Ca++ without adversely affecting their viability, alpha-Glucose-1-phosphate is also effective in removing ligatin-associated glycoproteins from intact cells. After eight of these treatments, the retinal cells seem not to exhibit Ca++-dependent adhesion for one another. It is thus suggested that ligatin in neural retina may serve as a baseplate for the attachment to the cell surface of glycoproteins active in Ca++-dependent adhesion. The finding that Ca++ serves to protect Ca++-dependent adhesion molecules from digestion by trypsin is discussed in relation to steric constraints on trypsin's accessibility to these adhesion molecules because of their possible binding to arrayed ligatin filaments.
D000818:Animals; D002118:Calcium / Q000494:pharmacology; D002448:Cell Adhesion / Q000187:drug effects; D002462:Cell Membrane / Q000378:metabolism; D002470:Cell Survival / Q000187:drug effects; D002642:Chick Embryo; D006023:Glycoproteins / Q000378:metabolism; D008565:Membrane Proteins / Q000378:metabolism / Q000502:physiology*; D010750:Phosphoproteins / Q000494:pharmacology*; D012160:Retina / Q000378:metabolism*; D013403:Sugar Phosphates / Q000494:pharmacology; D014357:Trypsin / Q000494:pharmacology
D006023:Glycoproteins; D008565:Membrane Proteins; D010750:Phosphoproteins; D013403:Sugar Phosphates; C013090:ligatin; D014357:Trypsin; D002118:Calcium