Coiled–coil targeting of myocilin to intracellular membranes

Characterization of the Intracellular Proteolytic Cleavage of Myocilin and Identification of Calpain II as a Myocilin-processing Protease

“…Caballero et al (56) found that a truncated myocilin containing the entire N-terminal domain and lacking most of the olfactomedin-like domain (amino acid residues 1-344) accumulated inside the cell. Recently, Stamer et al (57) found substantial FIGURE 11. Subcellular co-localization of myocilin and calpain II to the lumen of ER in transfected 293T cells using Optiprep gradient centrifugation.…”

Structure and Misfolding of the Flexible Tripartite Coiled-Coil Domain of Glaucoma-Associated Myocilin

“…Previously reported binding partners localized to the myocilin CC (Resch and Fautsch, 2009) could be experimental artifacts stemming from adhesiveness and should be reevaluated. Previous reports also indicate an association with lipid membranes (Stamer et al, 2006). Our data support the prior proposal that such association would be mediated by another membrane-bound protein (Stamer et al, 2006) because the negative electrostatic surface potential of mLZ 122-171 would prevent its direct insertion into the membrane.…”

“…Previous studies of myocilin have detected a tetramer, by crosslinking with glutaraldehyde (Nguyen et al, 1998) and non-reducing Western blot analysis (Gobeil et al, 2004), as well as a dimer (Dismuke et al, 2012; Fautsch and Johnson, 2001; Gobeil et al, 2004; Nguyen et al, 1998; Russell et al, 2001; Stamer et al, 2006) and higher ordered states (Dismuke et al, 2012; Fautsch et al, 2004; Russell et al, 2001). Based on our study, tetramerization occurs as a result of the amino acid sequence in the N-terminal stalk, and is independent of the disulfide bonds, which serve to stabilize individual dimers.…”

“…Myocilin is expressed at high levels in the trabecular meshwork (TM), an extracellular matrix in the anterior segment of the eye that forms part of the anatomical ultrafiltration system for aqueous humor (Abu-Hassan et al, 2014), and is a critical tissue for maintaining intraocular pressure (IOP) (Acott et al, 2014). The myocilin CC-containing region has been reported to interact with matrix components (Filla et al, 2002; Ueda et al, 2002; Wentz-Hunter et al, 2004), associate with membranes (Stamer et al, 2006), and confer its cell adhesion properties (Goldwich et al, 2009; Wentz-Hunter et al, 2004), but there is still much to learn about its structure and biological function. Myocilin is also associated with glaucoma (Polansky et al, 1997; Rozsa et al, 1998; Stone et al, 1997), a leading cause of blindness worldwide typically associated with elevated IOP (Quigley and Broman, 2006).…”

Intravitreal triamcinolone acetonide induced changes in the anterior segment in a pig model of branch retinal vein occlusion

“…Interestingly, the steroidinduced 55 kDa myocilin in porcine and human TM cells, referred to as Cort-GP several years ago [10], has subsequently been reported to be secreted (GIP 55 or TIGR) [19]. Myocilin has been associated with several other cell organelles including the nucleus and mitochondria [8,18,20], and also with exosome-like vesicles in TM cells [21]. Furthermore, mutant myocilin forms heterodimers with normal myocilin, and it has been speculated that retention of the mutant form may lead to endoplasmic reticulum overload, to form cell inclusions of heteromeric aggregates, similar to Russell bodies [22].…”