The Caenorhabditis elegans ASPP homolog APE-1 is a junctional protein phosphatase 1 modulator

• Published in: Genetics (Austin) 2022-08, Vol.222 (1)
• Main Authors: Beacham, Gwendolyn M, Wei, Derek T, Beyrent, Erika, Zhang, Ying, Zheng, Jian, Camacho, Mari M K, Florens, Laurence, Hollopeter, Gunther
• Format: Article
• Language: English
• Subjects: Animals; Ankyrins; Binding; Caenorhabditis elegans; Caenorhabditis elegans - metabolism; Cell junctions; Function analysis; Genetic screening; Genetics; Hominidae; Homology; Investigation; Kinases; Mass spectrometry; Mass spectroscopy; Mutation; Nematodes; Phosphatase; Phosphoprotein phosphatase; Proline; Proline - metabolism; Protein Binding; Protein phosphatase; Protein Phosphatase 1 - genetics; Protein Phosphatase 1 - metabolism; Proteins; Proteins - metabolism; Regulatory subunits; src Homology Domains; Structure-function relationships; Threonine; Vertebrates
• ISSN: 1943-2631; 0016-6731; 1943-2631
• DOI: 10.1093/genetics/iyac102

Abstract How serine/threonine phosphatases are spatially and temporally tuned by regulatory subunits is a fundamental question in cell biology. Ankyrin repeat, SH3 domain, proline-rich-region-containing proteins are protein phosphatase 1 catalytic subunit binding partners associated with cardiocutaneous diseases. Ankyrin repeat, SH3 domain, proline-rich-region-containing proteins localize protein phosphatase 1 catalytic subunit to cell–cell junctions, but how ankyrin repeat, SH3 domain, proline-rich-region-containing proteins localize and whether they regulate protein phosphatase 1 catalytic subunit activity in vivo is unclear. Through a Caenorhabditis elegans genetic screen, we find that loss of the ankyrin repeat, SH3 domain, proline-rich-region-containing protein homolog, APE-1, suppresses a pathology called “jowls,” providing us with an in vivo assay for APE-1 activity. Using immunoprecipitations and mass spectrometry, we find that APE-1 binds the protein phosphatase 1 catalytic subunit called GSP-2. Through structure–function analysis, we discover that APE-1’s N-terminal half directs the APE-1–GSP-2 complex to intercellular junctions. Additionally, we isolated mutations in highly conserved residues of APE-1’s ankyrin repeats that suppress jowls yet do not preclude GSP-2 binding, implying APE-1 does more than simply localize GSP-2. Indeed, in vivo reconstitution of APE-1 suggests the ankyrin repeats modulate phosphatase output, a function we find to be conserved among vertebrate homologs.