Our research is concerned with interactions among the transport-related proteins, primarily in the human red cell. We have carried out a number of studies, beginning about 1977, relating to interactions between the red cell anion exchange protein, band 3, and a number of other membrane and cytosolic proteins concerned with ion transport and its supply of metabolic fuel. Our initial investigations were devoted to relations among the glycolytic enzymes and their communication with band 3 and the Na+, K+-ATPase, which is the cation transport protein. Subsequently, as the identity and properties of the glucose transport protein (GLUT1) became clear, we began to study GLUT1 interactions with the anion and alkali cation transport proteins. These studies are carried out by rapid reaction methods based on the kinetics of fluorimetric probe interactions with membrane proteins. Meanwhile, other investigators made an extensive series of studies of the cytoskeleton and the links between cytoskeletal and membrane proteins, so that we could form a coherent view of the molecular organization in the plane below the membrane. As a result of these several strands of intellectual endeavor, we have proposed that the transport-related proteins form a transport network with cytoskeletal and cytosolic elements. The evidence supporting this general proposition is contained in the review article, cited below: 'Interactions between Band 3 and other Transport-related Proteins'. Recent compelling evidence now shows that the red cell water channel is a 28 kDa protein, CHIP28, which can conduct water into the cell with the requisite velocity, but is impermeable to urea and other uncharged small solutes. Since the relationship previously observed between band 3 and small solute permeation is based on effects of specific inhibitors of band 3 function and not upon imputed water transport, the role of band 3 in red cell transport remains to be explained. These studies are of general importance because isoforms of the red cell anion transporter and its cytoskeletal links are found in many other tissues including kidney and brain.

In addition to our other studies related to band 3, we are now addressing another crucial question about the molecular mechanism of solute transport into the human red cell. Does urea enter the red cell through the water channel? The transport of urea across the cell membrane is central to the preservation of the red cell integrity as the cells pass through the regions of high urea concentration in the kidney. This problem is addressed directly in the second review article (1993) given below. We have also recently found that red cell chloride transport is increased in subjects with AlzheimerÕs disease and are studying this process in detail.

Selected Publications:

Solomon, A.K. Interactions between band 3 and other transport-related proteins. Progress in Cell Research, Vol.2, pp. 269-283, Elsevier Science Publishers, Amsterdam (1992).

Solomon, A.K. Do water and urea cross the red cell membrane through the same channel? in Anion Transport in Leaky Epithelia, Benzon Symposium 34, pages 450-483, eds: H.H. Ussing, J. Fischbarg, O. Sten-Knudsen, E.H. Larsen, N. J. Willumsen; Munksgaard, Copenhagen 1993.

Toon, M.R., Solomon, A.K. (1994). Inhibition of red cell urea flux by anion exchange inhibitors. Biochim. Biophys. Acta. 1193, 276-286.