Membrane protein complexes
are major constituents of the fiber cell plasma membrane that function to
control the unique life long tissue physiology. Considerable proportion of
these complexes are implemented in cell-cell communication, which is critical
for lens homeostasis and transparency. Connexins, a classical type of communication
proteins forming molecular channels, which interconnect cytoplasm of neighboring
cells, has been shown to be a centerpiece of Gap Junctional Complexes. Our
data, obtained in collaboration with Kumar Lab at UIC demonstrated that these
complexes also include multifunctional adapter protein ZO1. Commonly found
in epithelial tight junctions ZO1 exhibits a complex translocation pattern
during fiber differentiation.
Aquaporin0 (MIP) form regular shaped square arrays, commonly found during EM imaging of fiber plasma membrane.
Adherence Junctional complexes provide structural integrity of lens fibers and lens in general. Until recently these abundant complexes formed by dosens of membrane proteins were largely overlooked by the research community. These complexes anchor cytoplasmic content to certain membrane microdomains supporting complex 3D envelope of the fiber’s plasma membrane.
A disintegrin/metalloprotease ADAM12 form microscopic plaque-like accumulations in fiber plasma membranes adjacent to gap junction complexes. This protein has multiple functions in mammalian tissues, but according to our data, in undifferentiated myoblasts and lens fibers ADAM12 is uniquely processed into 52 kDa isoform, implemented in membrane fusion. This may indicate that ADAM12 has a role in the core syncytium formation, that we recently characterized in the lens (in collaboration with Bassnett Lab at WashU). Few candidate membrane proteins are likely to be implemented in developmental cell-cell fusion. CD9, INT1B, CD47/MFR, TRAIL, Syncytin, ABC…, were reported to play role in mammalian developmental cell fusion but these data is still cell-type specific and controversial.