Disease relevance of SYNE1

• Mutations in SYNE1 lead to a newly discovered form of autosomal recessive cerebellar ataxia [1].
• Here, we report a newly discovered form of recessive ataxia in a French-Canadian cohort and show that SYNE1 mutations are causative in all of our kindreds, making SYNE1 the first identified gene responsible for a recessively inherited pure cerebellar ataxia [1].
• No MTX or CPG2 toxicity was observed [2].
• Carboxypeptidase G2 (CPG2), an enzyme produced by Pseudomonas strain RS-16, hydrolyzes the glutamate residue from methotrexate and other folates [3].
• The IC50 of the prodrug against LoVo colorectal tumor cells was 47 microM, and cleavage by CPG2 released the potent bis-iodo phenol mustard drug (IC50 = 0.34 microM) [4].

High impact information on SYNE1

• New partners include transcription repressors, an mRNA splicing regulator, a nuclear membrane protein named nesprin, nuclear myosin I and F-actin [5].
• The affinity of CPG2 for the substrate methotrexate was unaffected by three mutations required to prevent N-linked glycosylation [6].
• Cells expressing surface-tethered CPG2, however, became 16-24-fold more sensitive to CMDA and could mount a good bystander effect [6].
• These results provide definitive confirmation of previous correlative evidence that suggested a requirement of CPG-1-linked signaling for a number of fungal processes, including virulence and reproduction, while demonstrating that a second Galpha, CPG-2, is dispensable for these processes [7].
• The role of G protein-mediated signal transduction in fungal virulence was further examined by targeted disruption of the gene cpg-1, encoding CPG-1, and a second Galpha gene, cpg-2, encoding the subunit CPG-2 [7].

Chemical compound and disease context of SYNE1

• PURPOSE: This study was a pilot project to assess the safety and efficacy of carboxypeptidase G2 (CPG2) rescue from high-dose (HD) methotrexate (MTX) in patients with recurrent cerebral lymphoma [2].
• The glutamic acid is cleaved from the prodrug to form the active drug by carboxypeptidase G2 (CPG2), an enzyme from Pseudomonas sp., which is not found in mammalian cells [8].

Biological context of SYNE1

• The recognition that a characteristic muscle-specific mutant phenotype in the fly results from a disruption of its nesprin ortholog reinforces the candidacy of the human proteins for involvement in genetic diseases of skeletal and cardiac muscle [9].
• A nesprin-like protein is also encoded by the nematode genome [9].
• By comparing the sequence of the MDBK clone with sequence data from the human genome database, we have determined that this cDNA represents a central portion of a very large gene ( approximately 500 kb), encoding an approximately 25-kb transcript that we refer to as Syne-1 [10].
• CSF MTX concentration remained elevated for 4 hours after CPG2, and its decline followed first-order kinetics [2].
• The concentration of CPG2 required to decrease the cell count to 50% control for these cell lines was 3.5, 2.6, 26.6, and 7.9 x 10(-5) units/ml for CCRF-CEM, CCRF-CEM/E, CCRF-CEM/P, and CCRF-CEM/T, respectively [3].

Anatomical context of SYNE1

• Enaptin belongs to a family of recently identified giant proteins that associate with the F-actin cytoskeleton as well as the nuclear membrane [11].
• Antibodies against the ABD of Enaptin localise the protein at F-actin-rich structures throughout the cell and in focal contacts as well as at the nuclear envelope [11].
• Nesprin-1 is developmentally regulated in both smooth and skeletal muscle and is re-localized from the nuclear envelope to the nucleus and cytoplasm during C2C12 myoblast differentiation [12].
• We conclude that the Syne-1 gene is expressed in a variety of forms that are multifunctional and are capable of functioning at both the Golgi and the nuclear envelope, perhaps linking the two organelles during muscle differentiation [10].
• The location and structure of Syne-1 suggest that it may participate in the migration of myonuclei in myotubes and/or their anchoring at the postsynaptic apparatus [13].

Associations of SYNE1 with chemical compounds

• A blast search revealed that this clone overlaps with the 5' end of a recently identified spectrin family member Syne-1B/Nesprin-1beta, an alternately transcribed gene with muscle-specific forms that bind acetylcholine receptor and associate with the nuclear envelope [10].
• It consists of a conjugate of the F(ab')2 A5B7 antibody fragment and carboxypeptidase G2 (CPG2) and a prodrug, 4-[N,N-bis(2-iodoethyl)amino]phenoxycarbonyl L-glutamic acid [4].
• CONCLUSION: CPG2 rescue is a safe, effective alternative to leucovorin rescue after HD MTX and may prove particularly useful for the treatment of MTX-sensitive CNS tumors, as it does not affect CSF MTX levels [2].
• A synergistic cytotoxic effect of trimetrexate after simultaneous continuous exposure with CPG2 was observed with CCRF-CEM cells and with the three resistant cell lines [3].
• A benzoic acid mustard-glutamate prodrug was given when plasma enzyme levels had fallen to a predetermined safe level, and this was converted by CPG2 in the tumor into a cytotoxic form [14].

Physical interactions of SYNE1

• Binding was optimal for full nucleoplasmic dimers of nesprin-1alpha, since nesprin fragments SR1-5 and SR5-7 bound emerin as monomers with affinities of 53 nM and 250 mM, respectively [15].

Other interactions of SYNE1

• With the discovery of the actin-binding properties of Enaptin and the highly homologous Nuance, we define a family of proteins that integrate the cytoskeleton with the nucleoskeleton [11].
• In mature muscle, myne-1 and lamin A/C are perfectly colocalized, although colocalization with emerin is only partial [16].
• An association of this fragment with the C-terminal tail domain of the kinesin II subunit KIF3B was identified by yeast two-hybrid and co-precipitation assays, suggesting that the role of Syne-1 in cytokinesis involves an interaction with kinesin II [17].

Analytical, diagnostic and therapeutic context of SYNE1

• The adenovirus replicated and produced high levels of CPG2 in two different hepatocellular carcinoma xenografts (Hep3B and HepG2) but not other tissues [18].
• The role of the bystander effect in the treatment of a human breast carcinoma xenograft was studied by suicide gene therapy with carboxypeptidase G2 (CPG2) and CMDA [19].
• Using a modified comet assay, DNA interstrand cross links (ISC) were detected within 1 h of ZD2767P + CPG2 treatment and were repaired by 24 h [20].
• Athymic Nu/Nu mice with palpable transplanted human choriocarcinoma xenografts, which are resistant to conventional chemotherapy, were treated with anti-human chorionic gonadotropin antibodies conjugated to CPG2 [21].
• HPLC analysis was required to follow the reaction of DES-glutamate 5 with CPG2 [22].

References