Involvement of cell-cell adhesion in the expression of the cell cohesion molecule gp80 in Dictyostelium discoideum

Abstract

Soon after the initiation of the developmental cycle of Dictyostelium discoideum, cells acquire EDTA-sensitive cell-cell binding sites mediated by the glycoprotein gp24. Cells at the aggregation stage display a second type of cell adhesion site, the EDTA-resistant cell-cell binding sites, mediated by the glycoprotein gp80. The gene encoding gp80 is first turned on to a low basal level of expression in the preaggregation stage. At the onset of the aggregation stage, cells produce pulses of low levels of cAMP, which greatly augment the expression of gp80. To investigate the role of cell-cell adhesion in the regulation of gp80 expression, cells were developed in the presence of EDTA or carnitine to block the EDTA-sensitive cell binding sites. Alternatively, cell cohesion was disrupted by shaking low-density cultures at high shearing forces. In all three instances, gp80 was expressed at a substantially reduced level. In addition, exogenous cAMP pulses, which normally were capable of stimulating a precocious and enhanced expression of gp80, failed to restore the high level of gp80 expression. However, if the formation of cell-cell contact was permitted, exogenous cAMP pulses were able to rescue the expression of gp80 even when the cAMP signal relay was blocked. These results indicate that previous cell-cell contact, provided by the EDTA-sensitive binding sites, is required for the activation of the cAMP-mediated signal transduction pathway producing high levels of gp80 expression.

Cellular pattern formation during Dictyostelium aggregation

“…1, the homogeneous cell density is perturbed in the wavefront by about 10%. Thus we can expect travelling wave solutions of (2),( 5), (6) close to those of (1),(2), which is confirmed by numerical simulations (Fig. 3).…”

“…System (2), (6) with n = constant is identical to (1),(2), which has the properties of a classical excitable medium [ 1 1 ], and in particular exhibits periodic plane wave solutions [2]. We now look for periodic wave solutions to the full system (2),( 5), (6). They are governed by…”

“…To investigate the stability of wave propagation in the full model (2),( 5), (6) in two space dimensions, we add a small perturbation to the solutions of ( 7)-(9), n(x,y,t) =N(z) +h(z,y), u(x,y,t) =U(z) +a(z,y), v(x,y,t) =V(z) +O(z,y).…”

“…Cell streaming provides a primitive example of morphogenesis in an ensemble of communicating cells. It might have the functional significance of rapidly bringing cells in direct contact, which triggers developmental gene expression [6], and also of increasing the average cell velocity and thus the speed of aggregation. In this paper we are interested in a mechanistic explanation of this phenomenon.…”

Evolving social behavior through selection of single-cell adhesion in Dictyostelium discoideum

“…The adhesion system DdCAD-1 (gp24) is expressed soon after starvation and is inhibited by Ethylene Diamine Tetra acetic Acid (EDTA) ( Sriskanthadevan et al., 2011 ; Hou, 2004 ). Later, in the streaming and mound phases, polar cell adhesion by EDTA-resistant gp80 glycoproteins causes cells to organize in chains ( Fontana, 1993 ) and elicits activation of the cAMP-mediated signal transduction pathway ( Desbarats et al., 1994 ).…”