Dataset Information

The molecular basis of the Caskin1 and Mint1 interaction with CASK.

ABSTRACT: Calcium/calmodulin-dependent serine protein kinase (CASK) is a conserved multi-domain scaffolding protein involved in brain development, synapse formation, and establishment of cell polarity. To accomplish these diverse functions, CASK participates in numerous protein-protein interactions. In particular, CASK forms competing CASK/Mint1/Velis and CASK/Caskin1/Velis tripartite complexes that physically associate with the cytoplasmic tail of neurexin, a transmembrane protein enriched at presynaptic sites. This study shows that a short linear EEIWVLRK peptide motif from Caskin1 is necessary and sufficient for binding CASK. We also identified the conserved binding site for the peptide on the CASK calmodulin kinase domain. A related EPIWVMRQ peptide from Mint1 was also discovered to be sufficient for binding. Searching all human proteins for the Mint1/Caskin1 consensus peptide ExIWVxR revealed that T-cell lymphoma invasion and metastasis 1 (TIAM1) contains a conserved EEVIWVRRE peptide that was also found to be sufficient for CASK binding in vitro. TIAM1 is well known for its role in tumor metastasis, but it also possesses overlapping cellular and neurological functions with CASK, suggesting a previously unknown cooperation between the two proteins. This new peptide interaction motif also explains how Caskin1 and Mint1 form competing complexes and suggests a new role for the cellular hub protein CASK.

SUBMITTER: Stafford RL

PROVIDER: S-EPMC3158819 | biostudies-literature | 2011 Sep

REPOSITORIES: biostudies-literature

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The molecular basis of the Caskin1 and Mint1 interaction with CASK.

Stafford Ryan L RL Ear Jason J Knight Mary Jane MJ Bowie James U JU

Journal of molecular biology 20110712 1

Calcium/calmodulin-dependent serine protein kinase (CASK) is a conserved multi-domain scaffolding protein involved in brain development, synapse formation, and establishment of cell polarity. To accomplish these diverse functions, CASK participates in numerous protein-protein interactions. In particular, CASK forms competing CASK/Mint1/Velis and CASK/Caskin1/Velis tripartite complexes that physically associate with the cytoplasmic tail of neurexin, a transmembrane protein enriched at presynaptic ...[more]

PMID: 21763699

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Project description:Electron and charge transfers are part of many vital processes in nature and technology. Ab initio descriptions of these processes provide useful insights that can be utilized for applications. A combination of the embedded cluster material model and nonorthogonal configuration interaction (NOCI), in which the cluster wave functions are expanded in many-electron basis functions (MEBFs) consisting of spin-adapted, antisymmetrized products of multiconfigurational wave functions of fragments (which are usually molecules) in the cluster, appears to provide a compromise between accuracy and calculation time. Additional advantages of this NOCI-Fragments approach are the chemically convenient interpretation of the wave function in terms of molecular states, and the direct accessibility of electronic coupling between diabatic states to describe energy and electron transfer processes. Bottlenecks in this method are the large number of two-electron integrals that have to be handled for the calculation of an electronic coupling matrix element and the enormous number of matrix elements over determinant pairs that have to be evaluated for the calculation of one matrix element between the MEBFs. We show here how we created a reduced common molecular orbital basis that is utilized to significantly reduce the number of two-electron integrals that need to be handled. The results obtained with this basis do not show any loss of accuracy in relevant quantities like electronic couplings and vertical excitation energies. We also show a significant reduction in computation time without loss in accuracy when matrix elements over determinant pairs with small weights are neglected in the NOCI. These improvements in the methodology render NOCI-Fragments to be also applicable to treat clusters of larger molecular systems with larger atomic basis sets and larger active spaces, as the computation time becomes dependent on the number of occupied orbitals and less dependent on the size of the active space.

Project description:BackgroundHeterozygous loss-of-function mutations in the X-linked CASK gene cause progressive microcephaly with pontine and cerebellar hypoplasia (MICPCH) and severe intellectual disability (ID) in females. Different CASK mutations have also been reported in males. The associated phenotypes range from nonsyndromic ID to Ohtahara syndrome with cerebellar hypoplasia. However, the phenotypic spectrum in males has not been systematically evaluated to date.MethodsWe identified a CASK alteration in 8 novel unrelated male patients by targeted Sanger sequencing, copy number analysis (MLPA and/or FISH) and array CGH. CASK transcripts were investigated by RT-PCR followed by sequencing. Immunoblotting was used to detect CASK protein in patient-derived cells. The clinical phenotype and natural history of the 8 patients and 28 CASK-mutation positive males reported previously were reviewed and correlated with available molecular data.ResultsCASK alterations include one nonsense mutation, one 5-bp deletion, one mutation of the start codon, and five partial gene deletions and duplications; seven were de novo, including three somatic mosaicisms, and one was familial. In three subjects, specific mRNA junction fragments indicated in tandem duplication of CASK exons disrupting the integrity of the gene. The 5-bp deletion resulted in multiple aberrant CASK mRNAs. In fibroblasts from patients with a CASK loss-of-function mutation, no CASK protein could be detected. Individuals who are mosaic for a severe CASK mutation or carry a hypomorphic mutation still showed detectable amount of protein.ConclusionsBased on eight novel patients and all CASK-mutation positive males reported previously three phenotypic groups can be distinguished that represent a clinical continuum: (i) MICPCH with severe epileptic encephalopathy caused by hemizygous loss-of-function mutations, (ii) MICPCH associated with inactivating alterations in the mosaic state or a partly penetrant mutation, and (iii) syndromic/nonsyndromic mild to severe ID with or without nystagmus caused by CASK missense and splice mutations that leave the CASK protein intact but likely alter its function or reduce the amount of normal protein. Our findings facilitate focused testing of the CASK gene and interpreting sequence variants identified by next-generation sequencing in cases with a phenotype resembling either of the three groups.

Dataset Information

The molecular basis of the Caskin1 and Mint1 interaction with CASK.

Publications

The molecular basis of the Caskin1 and Mint1 interaction with CASK.

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