La. Sung et Wk. Lo, IMMUNODETECTION OF MEMBRANE SKELETAL PROTEIN-4.2 IN BOVINE AND CHICKEN EYE LENSES AND ERYTHROCYTES, Current eye research, 16(11), 1997, pp. 1127-1133
Purpose. Protein 4.2 is a major erythrocyte membrane skeletal protein,
playing an important role in maintaining the integrity and stability
of the membrane. It is a transglutaminase-like molecule with no enzyma
tic cross-linking activity. Several protein 4.2-associated proteins (i
.e. band 3, ankyrin, and protein 4.1) and transglutaminase activities
have been detected in the lens. The purpose of this study is to find o
ut if protein 4.2 is also expressed in lens fiber membranes. Methods.
Western blot analysis of cell membranes isolated from bovine and chick
en lens fibers and erythrocytes, and immunocytochemistry of frozen sec
tions of bovine and chicken lens fibers were carried out using two pro
tein 4.2-specific antibodies. These two peptide antibodies have been u
sed to identify two alternatively spliced protein 4.2 isoforms in huma
n erythrocyte membranes: the short (P4.2S, or hP4.2(691)) and the long
(P4.2L, or hP4.2(721)) isoforms. Results. Western blot analysis using
anti-P4.2(L) antibody demonstrated specific immunoreactive polypeptid
es in bovine and chicken lens fiber membranes and erythrocyte membrane
s, co-migrating with hP4.2(721). Immunofluorescence staining of bovine
and chicken lenses, using anti-P4.2(L) antibody, revealed specific si
gnals along the cell membranes of cortical fibers. The signals exhibit
ed a unique, patchy pattern along the cortical fiber cell membranes in
both cross-sectional and longitudinal views. In cross sections, the l
abeling of anti-P4.2(L) along the entire cell membranes gave an appear
ance of a hexagonal shape of fiber cells. Conclusions. Protein 4.2, or
its analogs, is present in the lens fiber membranes. Its specific sta
ining pattern in the lens fibers suggests that it participates in the
architecture of the lens fiber cell membranes, and may play a role in
the lens mechanics and pathology.