Altered N-glycosylation modulates TgrB1/TgrC1-mediated development but not allorecognition in Dictyostelium

Abstract

Cell surface adhesion receptors play diverse functions in multicellular development. In Dictyostelium, two immunoglobulin-like adhesion proteins, TgrB1 and TgrC1, are essential components with dual roles in morphogenesis and allorecognition during development. TgrB1 and TgrC1 form a heterophilic adhesion complex during cell contact and mediate intercellular communication. The underlying signaling pathways, however, have not been characterized. Here, we report on a mutation that suppresses the tgrB1/tgrC1-defective developmental arrest. The mutated gene alg9 encodes a putative mannosyl transferase that participates in N-linked protein glycosylation. We show that alteration in N-linked glycosylation, caused by alg9ins mutation or tunicamycin treatment, can partially suppress the developmental phenotypes caused by tgrC1 deletion or replacement with an incompatible allele. The alg9ins mutation also preferentially primed cells toward a stalk-cell fate. Despite its effect on development, we found that altered N-linked glycosylation had no discernable effect on TgrB1-TgrC1-mediated allorecognition. Our results show that N-linked protein glycosylation can modulate developmental processes without disturbing cell-cell recognition, suggesting that tgrB1 and tgrC1 have distinct effects in the two processes.