Gpr1, a Putative G-Protein-Coupled Receptor, Regulates Morphogenesis and Hypha Formation in the Pathogenic Fungus Candida albicans

Abstract

In response to various extracellular signals, the morphology of the human fungal pathogen Candida albicans switches from yeast to hypha form. Here, we report that GPR1 encoding a putative G-protein-coupled receptor and GPA2 encoding a G␣ subunit are required for hypha formation and morphogenesis in C. albicans. Mutants lacking Gpr1 (gpr1/gpr1) or Gpa2 (gpa2/gpa2) are defective in hypha formation and morphogenesis on solid hypha-inducing media. These phenotypic defects in solid cultures are suppressed by exogenously added dibutyryl-cyclic AMP (dibutyryl-cAMP). Biochemical studies also reveal that GPR1 and GPA2 are required for a glucose-dependent increase in cellular cAMP. An epistasis analysis indicates that Gpr1 functions upstream of Gpa2 in the same signaling pathway, and a two-hybrid assay reveals that the carboxyl-terminal tail of Gpr1 interacts with Gpa2. Moreover, expression levels of HWP1 and ECE1, which are cAMP-dependent hyphaspecific genes, are reduced in both mutant strains. These findings support a model that Gpr1, as well as Gpa2, regulates hypha formation and morphogenesis in a cAMP-dependent manner. In contrast, GPR1 and GPA2 are not required for hypha formation in liquid fetal bovine serum (FBS) medium. Furthermore, the gpr1 and the gpa2 mutant strains are fully virulent in a mouse infection. These findings suggest that Gpr1 and Gpa2 are involved in the glucose-sensing machinery that regulates morphogenesis and hypha formation in solid media via a cAMP-dependent mechanism, but they are not required for hypha formation in liquid medium or during invasive candidiasis.

Chemical screening identifies filastatin, a small molecule inhibitor of Candida albicans adhesion, morphogenesis, and pathogenesis

“…4E). Cells constitutively overexpressing the G protein-coupled receptor Gpr1 become hyperfilamentous on solid Spider media by PKA stimulation (26,28), and we observed that filastatin blocked hyphal morphogenesis in these cells (Fig. 4A).…”

Fungal Morphogenesis

“…CO 2 /HCO 3 2 directly stimulates Cyr1p activity by binding to the catalytic domain of Cyr1 (Klengel et al 2005). The cyclase activity is also regulated by the small GTPases (Ras1, Ras2), G-protein coupled receptor Gpr1, and Ga protein Gpa2 in response to nutrients (Feng et al 1999;Sanchez-Martinez and PerezMartin 2002;Miwa et al 2004;Maidan et al 2005a;Zhu et al 2009). Gpr1 in C. albicans is responsive to methionine, but not to glucose (Maidan et al 2005b), suggesting that this signal is likely encountered by this fungus in vivo.…”

The Flo8 Transcription Factor Is Essential for Hyphal Development and Virulence inCandida albicans

“…The cyclase activity is regulated by two G proteins, Ras1 and Gpa2, in C. albicans (Feng et al, 1999;Sanchez-Martinez and Perez-Martin, 2002;Miwa et al, 2004;Maidan et al, 2005). ras1 mutants are defective for hyphal formation under induction with serum filtrate in liquid media (Feng et al, 1999), whereas gpa2 mutants are defective in hyphal growth on solid hyphal-inducing media (Miwa et al, 2004;Maidan et al, 2005). The G proteins act through PKA to induce morphogenesis in C. albicans.…”

“…The adenylate cyclase Cdc35 and its associated protein Cap1 are required for hyphal development under all hyphal-inducing conditions, including serum (Bahn and Sundstrom, 2001;Rocha et al, 2001). The cyclase activity is regulated by two G proteins, Ras1 and Gpa2, in C. albicans (Feng et al, 1999;Sanchez-Martinez and Perez-Martin, 2002;Miwa et al, 2004;Maidan et al, 2005). ras1 mutants are defective for hyphal formation under induction with serum filtrate in liquid media (Feng et al, 1999), whereas gpa2 mutants are defective in hyphal growth on solid hyphal-inducing media (Miwa et al, 2004;Maidan et al, 2005).…”