Role of Matrix Metalloproteinase 3-mediated α-Synuclein Cleavage in Dopaminergic Cell Death

Abstract

Evidence suggests that the C-terminal truncation of ␣-synuclein is equally important as aggregation of ␣-synuclein in Parkinson disease (PD). Our previous results showed that an endopeptidase, matrix metalloproteinase-3 (MMP3), was induced and activated in dopaminergic (DA) cells upon stress conditions. Here, we report that MMP3 cleaved ␣-synuclein in vitro and in vivo and that ␣-synuclein and MMP3 were co-localized in Lewy bodies (LB) in the postmortem brains of PD patients. Incubation of ␣-synuclein with the catalytic domain of MMP3 (cMMP3) resulted in generation of several peptides, and the peptide profiles of WT ␣-synuclein (WTsyn) and A53T mutant (A53Tsyn) were different. Combined analysis using mass spectrometry and N-terminal determination revealed that MMP3 generated C-terminally truncated peptides of amino acids 1-78, 1-91, and 1-93 and that A53Tsyn produced significantly higher quantities of these peptides. Similar sizes of peptides were detected in N27 DA cells under oxidative stress and RNA interference to knock down MMP3-attenuated peptide generation. Co-overexpression of cMMP3 with either WTsyn or A53Tsyn led to a reduction in Triton X-100-insoluble aggregates and an increase in protofibril-like small aggregates. In addition, overexpression of the 1-93-amino acid peptide in the substantia nigra led to DA neuronal loss without LB-like aggregate formation. The results strongly indicate that MMP3 digestion of ␣-synuclein in DA neurons plays a pivotal role in the progression of PD through modulation of ␣-synuclein in aggregation, LB formation, and neurotoxicity.The epidemiological as well as animal studies suggest that environmental factors, genetic predispositions, and the interplay between the two factors are implicated in the PD 3 pathogenesis (1), although the underlying molecular mechanisms remain largely unknown. ␣-Synuclein is a major component of Lewy bodies (LB), the pathological hallmark of Parkinson disease (2). As expression of three mutant forms of ␣-synuclein, A53T, A30P, and E46K, in the brain (3-5) and increased copy number by duplication or triplication of the wild-type ␣-synuclein gene (6 -8) have been reported in the early onset familial cases of PD, the pathophysiological role of these mutants of ␣-synuclein has been a target of extensive investigations in PD research. The ability of ␣-synuclein to aggregate and form fibrillar deposits has been shown to play a central role in its pathology. The facts that the presence of C-terminally truncated ␣-synuclein in LB of sporadic PD and LB dementia (9, 10), the existence of various lengths of the truncated forms of ␣-synuclein in brain (10, 11), and the formation of C-terminally truncated ␣-synuclein in A53T transgenic mice that show motor symptoms (12) implicate the probable involvement of endopeptidases in cleaving ␣-synuclein in brains. In addition, about 15% of ␣-synuclein in LB are truncated forms, and incomplete degradation of ␣-synuclein produced highly amyloidogenic fragments (9, 13). Recent reports showed that matrix metalloprotei...

Reducing C-terminal truncation mitigates synucleinopathy and neurodegeneration in a transgenic model of multiple system atrophy

“…In this regard, we have previously shown a region-dependent alteration/expression of MMPs in the putamen and cortex of MSA patients (55). MMPs have been previously shown to cleave α-syn, thereby producing truncated forms (52,54). We here present an in vivo proof of concept of the ability of the caspase-1 inhibitor prodrug VX-765 to mitigate α-syn pathology and to mediate neuroprotection in an MSA mouse model.…”

“…Some studies have shown that C-terminally truncated α-syn is found in GCIs in MSA (48,49) as well as in Lewy bodies of PD and DLB patient brains (11,12,39,50,51). Several proteases such as calpain, matrix metalloproteases (MMPs), cathepsin D, and plasmin have been implicated in α-syn truncation, subsequently resulting in increased levels of protein aggregates; however, none has been established as a major producer of C-terminally truncated α-syn in vivo, especially in response to inflammation (12,39,42,(52)(53)(54)(55).…”

Human matrix metalloproteinases: An ubiquitarian class of enzymes involved in several pathological processes

“…This has important consequences since MMP-3 cleaves a-synuclein in vitro and in vivo and a-synuclein and MMP-3 co-localize in Lewy bodies (LB), as observed in post-mortem brains of PD patients (Choi et al, 2011). Evidence from in vitro investigations suggests that the MMP-3 mediated C-terminal truncation of a-synuclein releases fragments with the tendency to aggregate.…”

A deadly spread: cellular mechanisms of α-synuclein transfer

“…Alternately, if a-syn were enclosed in an exocytosed vesicle 10,15 or exosome, 14,49 as described above, the protein would be protected during its journey from extracellular enzymes. If unprotected, the risk for degradation is apparent as matrix metalloproteinase 3 has been shown to cleave both recombinant a-syn proteins 56,57 and neuroblastoma cell-secreted a-syn. 56 Recently, it was suggested that the molecular chaperone heat shock protein 70 (Hsp70) is released from cells together with a-syn and might modulate levels of extracellular a-syn oligomers.…”