Structure of cytochalasins and cytochalasin B binding sites in human erythrocyte membranes

Abstract

Twenty cytochalasins were tested for binding to and for inhibition of glucose transport in human erythrocyte membrane. In this membrane three cytochalasin B (CB) binding sites have been identified. All but three of the cytochalasins bind at site II. On the other hand, only nine of them, which are structurally closely related, bind at site I and inhibit glucose transport. For site I (and site III) binding and glucose transport inhibitory activities (a) the macrocyclic ring in the cytochalasin molecule must be at least 13-membered, (b) the nature of the aromatic ring at C-10 is not important, (c) the C-20-C-23 region makes a major contribution, and (d) the C-5-C-7 segment has a relatively minor influence. These findings do not support a proposed mechanism which involves 24, C-23, C-20, and C-1 oxygen atoms for interaction of CB with glucose carrier. The structural requirements for site II activity are less stringent. The size and the structure of the macrocyclic ring and the nature of the aromatic residue at C-10 modulate this activity only slightly, if at all. Modifications in the C-5-C-7 region of the molecule, however, result in substantial changes in this activity.

Specificity of glucose transport in Trypanosoma brucei

“…This contrast may be explained by the adaptation to physiological differences in the insect host with unstable and low glucose concentrations, or in the mammalian host where the intracellular parasite L. donovuni is not provided with the high and constant blood-glucose concentration available to the T. hrucei bloodstream form. The facilitated diffusion system we report here was less sensitive to cytochalasin B than was the erythrocyte-type glucose transporter in both blood and brain (Ki = 0.44 mM in T. hrucei versus Ki = 0.26-0.6 pM; Jung and Rampal, 1977;Rampal et al, 1980). Of the inhibitors tested, phloretin had the strongest effect on glucose transport in T. brucei and to our knowledge, this is the first time it has been reported for this organism.…”

Karyotypic “state” as a potential determinant for anticancer drug discovery

“…All cytochalasins bind actin and alter its polymerization, but cytochalasin D is ten times more active than cytochalasin B (22). Additionally, cytochalasins A and B bind to glucose transporters, but cytochalasins D, E, and H do not (23), implying that there are, in fact, distinct subgroups of cytochalasins. Their cytotoxic effects are consistent with this distinction.…”

Effect of glucose transport inhibitors on vincristine efflux in multidrug-resistant murine erythroleukaemia cells overexpressing the multidrug resistance-associated protein (MRP) and two glucose transport proteins, GLUT1 and GLUT3

“…Vincristine steady-state accumulation studies VCR accumulation was assayed in 106 cells ml-' after 60 min incubation in PBS using 25 nm [G-3H] The concentration of CB used in these experiments was specific for glucose transport inhibition and minimized other non-glucose transport affinity binding and actin binding (Rampal et al, 1980). CE has a low binding affinity for glucose transport proteins and was used as a control to demonstrate a specific glucose transporter binding by cytochalasin B (Vera et al, 1991).…”

“…The motif AxLxxxxxxxxxxxxxG aligned to the putative CB-binding domains on GLUT1 and amino acid) was found within the mouse MRP (R Deeley, personal iication), human MRP (Cole et al, 1992), mouse GLUT1 (Kaestner et GLUT3 using Gap: (1) mouse CFTR; (2) mouse P-glycoprotein ),mouse GLUT3 (Nagamatsu et al, 1992) and mouse GLUT4 (mdrl but not mdr3); (4) Leishmania P-gpA; (5) (Rampal et al, 1980;Vera et al, 1991). hydrophilic region ( Figure 5B).…”