Single-cell fluidic force microscopy reveals stress-dependent molecular interactions in yeast mating

Abstract

Sexual agglutinins of the budding yeast Saccharomyces cerevisiae are proteins mediating cell aggregation during mating. Complementary agglutinins expressed by cells of opposite mating types “a” and “α” bind together to promote agglutination and facilitate fusion of haploid cells. By means of an innovative single-cell manipulation assay combining fluidic force microscopy with force spectroscopy, we unravel the strength of single specific bonds between a- and α-agglutinins (~100 pN) which require pheromone induction. Prolonged cell–cell contact strongly increases adhesion between mating cells, likely resulting from an increased expression of agglutinins. In addition, we highlight the critical role of disulfide bonds of the a-agglutinin and of histidine residue H273 of α-agglutinin. Most interestingly, we find that mechanical tension enhances the interaction strength, pointing to a model where physical stress induces conformational changes in the agglutinins, from a weak-binding folded state, to a strong-binding extended state. Our single-cell technology shows promises for understanding and controlling the complex mechanism of yeast sexuality.

Cell–Cell Mating Interactions: Overview and Potential of Single-Cell Force Spectroscopy

“…In yeasts, the cell-cell interactions are actuallystrengthened under tensile force. This technique can now assay enough cell pairs to allow phenotypic characterization of the interactions between cells with specific mutations or gene deletions in known or putative adhesins [36,69] or differences in surface expression levels [36]. What else lies ahead?…”

“…As such, FluidFM-based SCFS was recently applied to study adhesive interactions in yeast mating by bringing a pair of MATα and MATa cells in contact while meticulously controlling contact force and time [36]. Subsequent pulling revealed the forced extension and unbinding behavior of single interacting α-agglutinin/a-agglutinin partners [36].…”

“…As such, FluidFM-based SCFS was recently applied to study adhesive interactions in yeast mating by bringing a pair of MATα and MATa cells in contact while meticulously controlling contact force and time [36]. Subsequent pulling revealed the forced extension and unbinding behavior of single interacting α-agglutinin/a-agglutinin partners [36]. Under minimal contact time (0.1 s) and contact force (0.25 nN) conditions, a relatively weak single bond strength of approximately 100 pN was observed for pheromone-induced cells.…”

“…Ovum; 2 spermatozoid; 3 phosphatidyl ethanolamine; 4 mating pair stabilization; 5 reference[36] is the first report of the use of AFM single-cell force spectroscopy to study adhesive interactions in a mating system.…”

Review: Advanced Atomic Force Microscopy Modes for Biomedical Research

“…Such manipulation capabilities allow researchers to modify biomedical samples on the nanoscopic scale, which is much more precise compared to conventional needle-based micro-manipulation systems. This is a particularly convenient capability for cellular biophysics studies [ 122 ], such as cellular adhesive interactions [ 123 , 124 ], stress-dependent yeast cell mating [ 125 ], and cellular detachment forces and energies [ 126 ].…”