Critical role for PAR1 in kallikrein 6‐mediated oligodendrogliopathy

Abstract

Kallikrein 6 (Klk6) is a secreted serine protease preferentially expressed by oligodendroglia in CNS white matter. Elevated levels of Klk6 occur in actively demyelinating multiple sclerosis (MS) lesions and in cases of spinal cord injury (SCI), stroke and glioblastoma. Taken with recent evidence establishing Klk6 as a CNS-endogenous activator of protease-activated receptors (PARs), we hypothesized that Klk6 activates a subset of PARs to regulate oligodendrocyte physiology and potentially pathophysiology. Here, primary oligodendrocyte cultures derived from wild type or PAR1-deficient mice and the murine oligodendrocyte cell line, Oli-neu, were used to demonstrate that Klk6 mediates loss of oligodendrocyte processes and impedes morphological differentiation of oligodendrocyte progenitor cells (OPCs) in a PAR1-dependent fashion. Comparable gliopathy was also elicited by the canonical PAR1 agonist, thrombin, as well as PAR1-activating peptides (PAR1-APs). Klk6 also exacerbated ATP-mediated oligodendrogliopathy in vitro, pointing to a potential role in augmenting excitotoxicity. In addition, Klk6 suppressed the expression of proteolipid protein (PLP) RNA in cultured oligodendrocytes by a mechanism involving PAR1-mediated Erk1/2 signaling. Microinjection of PAR1 agonists, including Klk6 or PAR1-APs, into the dorsal column white matter of PAR+/+ but not PAR−/− mice promoted vacuolating myelopathy and a loss of immunoreactivity for myelin basic protein (MBP) and CC-1+ oligodendrocytes. These results demonstrate a functional role for Klk6-PAR1 signaling in oligodendroglial pathophysiology and suggest that PAR1 or PAR1-agonists may represent new targets to moderate demyelination and to promote myelin regeneration in cases of CNS white matter injury or disease.

Interplay between exercise and dietary fat modulates myelinogenesis in the central nervous system

“…RNA was isolated from that half of the unfixed lumbosacral spinal cord not used for protein extraction using RNA STAT-60 (Tel-Test, Friendswood, TX). The relative amount of RNA in each case was determined in 0.10 μg of RNA using an iCycler iQ5 system (BioRad) and the probes (Thermo Fisher Scientific, Waltham, MA) and primers (Integrated DNA Technologies, Coralville, IA) described in Table 1 (Burda et al 2013). The relative amount of RNA in each case was normalized to the constitutively expressed gene Rn18S.…”

Kallikreins – The melting pot of activity and function

“…Elevated levels of KLK6 are detected in active multiple sclerosis lesions and patient sera [149]. In addition to cleaving myelin proteins such as the myelin basic protein, KLK6 can cleave components of the blood–brain barrier, such as laminin, fibronectin and collagens, and can induce inflammation via the activation of cell-surface PARs [150]. Studies show that PAR2 modulates neuro-inflammation by enhancing demyelination and that application of KLK6-inactivating antibodies can reduce the pathobiological role of KLK6 [151, 152].…”

Differential expression of multiple kallikreins in a viral model of multiple sclerosis points to unique roles in the innate and adaptive immune response

“…The first potential link between KLK6 and demyelinating disease were studies showing its dense expression by myelin producing oligodendrocytes (Scarisbrick et al 1997; Scarisbrick et al 2000; Scarisbrick et al 2001) coupled with its ability to rapidly hydrolyze major myelin and blood brain barrier proteins (Bernett et al 2002; Blaber et al 2002; Scarisbrick et al 2002; Blaber et al 2004; Angelo et al 2006), and to promote oligodendrogliopathy (Scarisbrick et al 2002; Burda et al 2013), neuronal injury (Scarisbrick et al 2008; Radulovic et al 2013; Yoon et al 2013), and astrogliosis (Vandell et al 2008; Scarisbrick et al 2012). Furthermore, KLK6 is elevated in activated T-cells, and those treated with steroid hormones such as glucocorticoids, androgens or progesterone (Scarisbrick et al 2002; Blaber et al 2004; Christophi et al 2004; Scarisbrick et al 2006; Scarisbrick et al 2012).…”

“…Furthermore, KLK6 is elevated in activated T-cells, and those treated with steroid hormones such as glucocorticoids, androgens or progesterone (Scarisbrick et al 2002; Blaber et al 2004; Christophi et al 2004; Scarisbrick et al 2006; Scarisbrick et al 2012). More recently, the cellular effects of KLK6 across the neural-immune axis were linked to activation of protease activated receptors 1 (PAR1) and 2 (PAR2), including its actions in axonopathy (Radulovic et al 2013; Yoon et al 2013), oligodendrogliopathy (Burda et al 2013), astrogliosis (Vandell et al 2008; Scarisbrick et al 2012) and lymphocyte survival (Scarisbrick et al 2011). Of critical importance, KLK6-neutralizing antibodies attenuate neuroinflammatory and neurodegenerative changes in the spinal cord of mice with proteolipid protein- or myelin oligodendrocyte glycoprotein-mediated experimental autoimmune encephalomyelitis (Blaber et al 2004), in addition to those with TMEV-induced inflammatory demyelinating disease (Scarisbrick et al 2012).…”