Reference: Kruth KA and Rubenstein PA (2012) Two deafness-causing (DFNA20/26) actin mutations affect Arp2/3-dependent actin regulation. J Biol Chem 287(32):27217-26

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Abstract


Hearing requires proper function of the auditory hair cell, which is critically dependent upon its actin-based cytoskeletal structure. Currently, ten point mutations in nonmuscle γ-actin have been identified as causing progressive autosomal dominant nonsyndromic hearing loss (DFNA20/26), highlighting these ten residues as functionally important to actin structure and/or regulation. Two of the mutations, K118M and K118N, are located near the putative binding site for the ubiquitously expressed Arp2/3 complex. We therefore hypothesized that these mutations may affect Arp2/3-dependent regulation of the actin cytoskeleton. Using in vitro bulk polymerization assays, we show that the Lys-118 mutations notably reduce actin + Arp2/3 polymerization rates compared with WT. Further in vitro analysis of the K118M mutant using TIRF microscopy indicates the actual number of branches formed per filament is reduced compared with WT and, surprisingly, branch location is altered such that the majority of K118M branches form near the pointed end of the filament. These results highlight a previously unknown role for the Lys-118 residue in the actin-Arp2/3 interaction and also further suggest that Lys-118 may play a more significant role in intra- and intermonomer interactions than was initially hypothesized.

Reference Type
Journal Article | Research Support, N.I.H., Extramural
Authors
Kruth KA, Rubenstein PA
Primary Lit For
ACT1 | Actin-related protein 2/3 complex
Additional Lit For
ARP3 | ARP2 | act1-K118M | act1-K118N

Phenotype Annotations 2 entries for 1 gene


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GenePhenotypeExperiment TypeMutant InformationStrain BackgroundChemicalDetails
ACT1actin cytoskeleton morphology: abnormal
classical genetics reduction of function
Allele: act1-K118M
OtherDetails: K118M cables are fragmented and lack any dominant orientation, resulting in a meshwork
ACT1actin cytoskeleton morphology: abnormal
classical genetics reduction of function
Allele: act1-K118N
OtherDetails: K118N cables appear to maintain some mother-to-bud polarity, but are still notably more disorganized and random
Showing 1 to 2 of 2 entries

Disease Annotations


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Gene Disease Ontology Term Qualifier Evidence Method Source Assigned On Reference