The <i>Saccharomyces cerevisiae</i> Ssy5 signaling protease is a core component of the plasma membrane (PM)-localized SPS (Ssy1-Ptr3-Ssy5) sensor<i>.</i> In response to extracellular amino acids, the SPS-sensor orchestrates the proteasomal degradation of the inhibitory Ssy5 prodomain.
Evidence from multiple laboratories has implicated Ssy1, a nontransporting amino acid permease, as the receptor component of the yeast plasma membrane (PM)-localized SPS (Ssy1-Ptr3-Ssy5)-sensor.
We retrospectively analyzed the clinical data and outcomes of ten patients with the clinical diagnosis of anti-GAD65 positive SPS in which TPE was employed to improve symptoms refractory to conventional treatment during an eight-year period.
Since GAD65 is intracellularly located and associated with type 1 diabetes mellitus and different clinical neurological phenotypes such as CA, stiff-person syndrome, and epilepsy, some researchers have argued that anti-GAD65 Abs have no pathogenic roles.
Stiff person syndrome (SPS) is a rare and challenging neuromuscular junction disorder with typical musculoskeletal manifestations associated with anti-GAD65 antibodies, extra rheumatological manifestations, including neuropsychiatric symptoms and severe dysautonomic troubles.
We present a case of a 65-year-old African American male, immunosuppressed on Tacrolimus, who initially presented with cerebellar ataxia and rapidly developed Progressive Encephalomyelitis with Rigidity and Myoclonus (PERM) with positive anti-glutamic acid decarboxylase (GAD65) antibodies, no underlying malignancy, and normal neuroimaging.
Although immunization with GAD65 did not produce any behavioral abnormality in the mice, the induction of neuronal-surface antibodies and the trend towards loss of GABAergic neurons in the brainstem, supports a role for humoral autoimmunity in the pathogenesis of SPS and suggests that the mechanisms may involve spread to antigens expressed on the surface of these neurons.
One explanation for these data is the differences in epitope engagement between the anti-GAD reactivity in SPS and T1D: in both diseases, anti-GAD antibody reactivity is predominantly to a conformational epitope region in the PLP- and C-terminal domains of the 65 kDa isoform but, additionally in SPS, there is reactivity to conformational epitope(s) on GAD67, and short linear epitopes in the C-terminal region and at the N-terminus of GAD65.
This result is interesting because auto-antibodies to GAD67 and the more widely studied GAD65 homologue encoded by the GAD2 gene, are described in patients with Stiff-Person Syndrome (SPS), epilepsy, cerebellar ataxia and Batten disease.
In study A we tested sera from 52 normal subjects, 25 newly diagnosed type 1 diabetics and 3 stiff man syndrome (SMS) subjects detecting GAD65 autoantibodies in 72% of IDDM and 100% of SMS patients.
Thus, destruction of pancreatic beta cells, which results in insulin-dependent diabetes mellitus (IDDM), and impairment of GABA-ergic synaptic transmission in Stiff-Man syndrome (SMS) are both characterized by circulating autoantibodies to GAD65.
The aim of the study was to examine the genetic linkage of this selected risk haplotype with single nucleotide variations (SNVs) in the coding sequence of the GP6 gene in order to identify possible functional SNVs in association with SPS and fetal loss.
The objectives of the present study were to assess the genetic variability of the GP6 gene in patients with platelet hyperaggregability phenotype, known as sticky platelet syndrome (SPS) manifesting as deep vein thrombosis (DVT), and/or pulmonary embolism, and in controls; and to evaluate its role in the pathogenesis of venous thromboembolism (VTE) in SPS.
We found a higher occurrence of three SNPs of the GP6 gene in SPS patients versus control subjects (rs1671153: 0.204 vs. 0.048, odds ratio [OR] 5.116, 95% confidence interval [CI] 1.536-17.03; rs1654419: 0.204 vs. 0.071, OR 3.326, 95% CI 1.149-9.619; rs1613662: 0.204 vs. 0.071, OR 3.326, 95% CI 1.149-9.619).
Our results, especially higher occurrence of four haplotypes in SPS patients, can support an idea that variability of the GP6 gene may be associated with the platelet hyperaggregability in SPS.
As there are only a few cases in the literature similar to this one, highlighting the successful treatment of anti-GAD ab cerebellar ataxia and SPS with dual therapy (steroids followed by IVIG) is important.
Another explanation for disease expressions in SPS includes ready access of anti-GAD to antigen sites due to immune responsiveness within the CNS itself according to intrathecal anti-GAD-specific B cells and autoantibody.