Formation of immunoglobulin light chain amyloid oligomers in primary cutaneous nodular amyloidosis

Significance of Oligomeric and Fibrillar Species in Amyloidosis: Insights into Pathophysiology and Treatment

Amyloidosis is a term referring to a group of various protein-misfolding diseases wherein normally soluble proteins form aggregates as insoluble amyloid fibrils. How, or whether, amyloid fibrils contribute to tissue damage in amyloidosis has been the topic of debate. In vitro studies have demonstrated the appearance of small globular oligomeric species during the incubation of amyloid beta peptide (Aβ). Nerve biopsy specimens from patients with systemic amyloidosis have suggested that globular structures similar to Aβ oligomers were generated from amorphous electron-dense materials and later developed into mature amyloid fibrils. Schwann cells adjacent to amyloid fibrils become atrophic and degenerative, suggesting that the direct tissue damage induced by amyloid fibrils plays an important role in systemic amyloidosis. In contrast, there is increasing evidence that oligomers, rather than amyloid fibrils, are responsible for cell death in neurodegenerative diseases, particularly Alzheimer’s disease. Disease-modifying therapies based on the pathophysiology of amyloidosis have now become available. Aducanumab, a human monoclonal antibody against the aggregated form of Aβ, was recently approved for Alzheimer’s disease, and other monoclonal antibodies, including gantenerumab, solanezumab, and lecanemab, could also be up for approval. As many other agents for amyloidosis will be developed in the future, studies to develop sensitive clinical scales for identifying improvement and markers that can act as surrogates for clinical scales should be conducted.

Primary localized cutaneous nodular amyloidosis presenting as lymphatic malformation: A case report

Primary skin amyloidosis is a chronic skin disease in which amyloid deposits in the normal skin tissues without involving other organs. At present, the causes and mechanisms of morbidity have not been fully elucidated. There are few clinical reports of nodular skin amyloidosis, and the domestic reports are mostly limited cases. This study reported a rare case of a 46-year-old woman with primary localized cutaneous nodular amyloidosis (PLCNA). The patient presented with features of lymphatic malformation, a plexiform nodule of small blisters. Histological examination revealed amyloid deposits involving the superficial and deep dermis with a small number of plasma cells. Further examinations did not reveal evidence of systemic involvement, indicating a PLCNA. The presentation as lymphatic malformation lesions illustrates the importance of clinical pathology. Nodular amyloidosis typically manifests as single or multiple yellow-brown nodules or plaques of a few millimeters to several centimeters. The center of the nodule sometimes shows atrophy and relaxation or forms a bullous. It is recommended to perform a pathological examination to confirm the diagnosis to distinguish it from lymphatic malformation.

Proteomics of Multiple Sclerosis: Inherent Issues in Defining the Pathoetiology and Identifying (Early) Biomarkers

Multiple Sclerosis (MS) is a demyelinating disease of the human central nervous system having an unconfirmed pathoetiology. Although animal models are used to mimic the pathology and clinical symptoms, no single model successfully replicates the full complexity of MS from its initial clinical identification through disease progression. Most importantly, a lack of preclinical biomarkers is hampering the earliest possible diagnosis and treatment. Notably, the development of rationally targeted therapeutics enabling pre-emptive treatment to halt the disease is also delayed without such biomarkers. Using literature mining and bioinformatic analyses, this review assessed the available proteomic studies of MS patients and animal models to discern (1) whether the models effectively mimic MS; and (2) whether reasonable biomarker candidates have been identified. The implication and necessity of assessing proteoforms and the critical importance of this to identifying rational biomarkers are discussed. Moreover, the challenges of using different proteomic analytical approaches and biological samples are also addressed.

Preparation and Characterization of Tau Oligomer Strains

An increasing number of studies have demonstrated the existence of multiple conformational entities of tau, as have been observed for prion protein. We have developed and optimized techniques to isolate and study oligomeric tau strains both in vitro and ex vivo. Moreover, we have modified protocols that demonstrate the seeding properties of oligomeric tau strains that are capable of propagating in vivo. These methods and protocols are explained in this chapter.

Nodular amyloidosis: clinical recognition of an unusual entity

Nodular amyloidosis is a protein deposition disorder that is important to recognize in the clinical setting. Identification and differentiation from primary systemic amyloidosis, which has an identical cutaneous presentation, but serious systemic implications, is of particular significance. Our case report highlights two patients who presented with isolated involvement of the plantar surface and ungual phalanges, each with concomitant tinea pedis. Recognition and diagnosis of cutaneous amyloidosis enables discrimination from systemic disease, and if found, prompt institution of appropriate treatment.

Structural, morphological, and functional diversity of amyloid oligomers

Protein misfolding and aggregation are known to play a crucial role in a number of important human diseases (Alzheimer's, Parkinson's, prion, diabetes, cataracts, etc.) as well as in a multitude of physiological processes. Protein aggregation is a highly complex process resulting in a variety of aggregates with different structures and morphologies. Oligomeric protein aggregates (amyloid oligomers) are formed as both intermediates and final products of the aggregation process. They are believed to play an important role in many protein aggregation-related diseases, and many of them are highly cytotoxic. Due to their instability and structural heterogeneity, information about structure, mechanism of formation, and physiological effects of amyloid oligomers is sparse. This review attempts to summarize the existing information on the major properties of amyloid oligomers.

Using intramolecular disulfide bonds in tau protein to deduce structural features of aggregation-resistant conformations

Because tau aggregation likely plays a role in a number of neurodegenerative diseases, understanding the processes that affect tau aggregation is of considerable importance. One factor that has been shown to influence the aggregation propensity is the oxidation state of the protein itself. Tau protein, which contains two naturally occurring cysteine residues, can form both intermolecular disulfide bonds and intramolecular disulfide bonds. Several studies suggest that intermolecular disulfide bonds can promote tau aggregation in vitro. By contrast, although there are data to suggest that intramolecular disulfide bond formation retards tau aggregation in vitro, the precise mechanism underlying this observation remains unclear. While it has been hypothesized that a single intramolecular disulfide bond in tau leads to compact conformations that cannot form extended structure consistent with tau fibrils, there are few data to support this conjecture. In the present study we generate oxidized forms of the truncation mutant, K18, which contains all four microtubule binding repeats, and isolate the monomeric fraction, which corresponds to K18 monomers that have a single intramolecular disulfide bond. We study the aggregation propensity of the oxidized monomeric fraction and relate these data to an atomistic model of the K18 unfolded ensemble. Our results argue that the main effect of intramolecular disulfide bond formation is to preferentially stabilize conformers within the unfolded ensemble that place the aggregation-prone tau subsequences, PHF6* and PHF6, in conformations that are inconsistent with the formation of cross-β-structure. These data further our understanding of the precise structural features that retard tau aggregation.