New insights into regulation of erythrocyte shape.

Two ideas explain the mechanism of shape regulation: the lipid bilayer coupled theory and the protein network scaffold theory. Recently, several important articles have been published on the former theory. However, many phenomena argue against the theory, including behavior of ghosts and triton shells, various types of manipulation of proteins, and fixation of the shape by the addition of large reagents outside the cell. Moreover, hereditary spherocytosis shows normal, uneven distribution of phospholipids, and hereditary and artificial defects of a membrane protein show spherocytes or elliptocytes. The liquid state of the lipid layer does not seem to support the shape or mechanical characteristics. On the other hand, all of these phenomena argue for the protein network scaffold theory. Characteristics of each protein and interactions among proteins are now being clarified, but this theory and the author's own ideas still lack decisive evidence.