Aspergillus nidulans CkiA is an essential casein kinase I required for delivery of amino acid transporters to the plasma membrane

Abstract

Summary Type I casein kinases are highly conserved among Eukaryotes. Of the two Aspergillus nidulans casein kinases I, CkiA is related to the δ/ε mammalian kinases and to Saccharomyces cerevisiæ Hrr25p. CkiA is essential. Three recessive ckiA mutations leading to single residue substitutions, and downregulation using a repressible promoter, result in partial loss‐of‐function, which leads to a pleiotropic defect in amino acid utilization and resistance to toxic amino acid analogues. These phenotypes correlate with miss‐routing of the YAT plasma membrane transporters AgtA (glutamate) and PrnB (proline) to the vacuole under conditions that, in the wild type, result in their delivery to the plasma membrane. Miss‐routing to the vacuole and subsequent transporter degradation results in a major deficiency in the uptake of the corresponding amino acids that underlies the inability of the mutant strains to catabolize them. Our findings may have important implications for understanding how CkiA, Hrr25p and other fungal orthologues regulate the directionality of transport at the ER‐Golgi interface.

Application of a New Dual Localization-Affinity Purification Tag Reveals Novel Aspects of Protein Kinase Biology in Aspergillus nidulans

“…As recently reported, CkiA Hrr25 was weakly enriched in interphase nuclei [111] but high resolution confocal time lapse imaging revealed other cell cycle specific locations (Figure 9). As cells entered mitosis CkiA Hrr25 concentrated to a single nuclear focus which subsequently segregated into two foci (Figure 9A–D).…”

“…The essential CkiA Hrr25 -DLAP casein kinase 1 (CK1) located to multiple cell structures consistent with the diverse functions of this kinase family including roles in trafficking amino acid transporters to the plasma membrane in A. nidulans [5], [111]–[114]. As recently reported, CkiA Hrr25 was weakly enriched in interphase nuclei [111] but high resolution confocal time lapse imaging revealed other cell cycle specific locations (Figure 9).…”

The Genomes of Three Uneven Siblings: Footprints of the Lifestyles of Three Trichoderma Species

“…14). The A. nidulans homolog of CK1a, CkiA, was found to be essential and involved in amino acid utilization and resistance to toxic amino acid analogs, which is likely due to a mislocalization of amino acid transporters (754). Amino acid utilization and metabolism were shown to be connected to regulation of plant cell wall degradation in T. reesei and N. crassa (351,415,(755)(756)(757).…”

The Aspergillus nidulans Proline Permease as a Model for Understanding the Factors Determining Substrate Binding and Specificity of Fungal Amino Acid Transporters

“…Consistently with previous Western blots (22), all PrnB-GFP alleles detected by in-gel fluorescence appear as doublets. Moreover, the lower molecular weight fast migrating bands that were also detected most probably correspond to N-terminal degradation products, as it has been observed for AgtA, another YAT of A. nidulans (60). In-gel fluorescence analysis (Figs.…”

“…To examine whether AZC, Ala, Gly, and GABA, apart from inhibiting L-[ 3 H]proline transport, could also be transported by the PrnB mutants, we made use of the genetic tractability of A. nidulans, which can utilize L-alanine, glycine, and GABA as sole nitrogen and/or carbon sources. Given that the permease(s) of A. nidulans involved in L-alanine and glycine transport are not known, we made use of a CkiA (casein kinase I) allele, which has been previously shown to be necessary for the plasma membrane targeting of amino acid transporters (60). The ckiA1919 mutation does not significantly affect prnB-dependent growth on L-proline, but confers severely impaired growth on many other amino acids, including glycine and L-alanine (Fig.…”