Intracellular calreticulin regulates multiple steps in fibrillar collagen expression, trafficking, and processing into the extracellular matrix.

Calreticulin (CRT), a chaperone and Ca(2+) regulator, enhances wound healing, and its expression correlates with fibrosis in animal models, suggesting that CRT regulates production of the extracellular matrix. However, direct regulation of collagen matrix by CRT has not been previously demonstrated. We investigated the role of CRT in the regulation of fibrillar collagen expression, secretion, processing, and deposition in the extracellular matrix by fibroblasts. Mouse embryonic fibroblasts deficient in CRT (CRT(-/-) MEFs) have reduced transcript levels of fibrillar collagen I and III and less soluble collagen as compared with wild type MEFs. Correspondingly, fibroblasts engineered to overexpress CRT have increased collagen type I transcript and protein. Collagen expression appears to be regulated by endoplasmic reticulum (ER) calcium levels and intracellular CRT, because thapsigargin treatment reduced collagen expression, whereas addition of exogenous recombinant CRT had no effect. CRT(-/-) MEFs exhibited increased ER retention of collagen, and collagen and CRT were co-immunoprecipitated from isolated cell lysates, suggesting that CRT is important for trafficking of collagen through the ER. CRT(-/-) MEFs also have reduced type I procollagen processing and deposition into the extracellular matrix. The reduced collagen matrix deposition is partly a consequence of reduced fibronectin matrix formation in the CRT-deficient cells. Together, these data show that CRT complexes with collagen in cells and that CRT plays critical roles at multiple stages of collagen expression and processing. These data identify CRT as an important regulator of collagen and suggest that intracellular CRT signaling plays an important role in tissue remodeling and fibrosis.

The calreticulin-binding sequence of thrombospondin 1 regulates collagen expression and organization during tissue remodeling.

Amino acids 17-35 of the thrombospondin1 (TSP1) N-terminal domain (NTD) bind cell surface calreticulin to signal focal adhesion disassembly, cell migration, and anoikis resistance in vitro. However, the in vivo relevance of this signaling pathway has not been previously determined. We engineered local in vivo expression of the TSP1 calreticulin-binding sequence to determine the role of TSP1 in tissue remodeling. Surgical sponges impregnated with a plasmid encoding the secreted calreticulin-binding sequence [NTD (1-35)-EGFP] or a control sequence [mod NTD (1-35)-EGFP] tagged with enhanced green fluorescent protein were implanted subcutaneously in mice. Sponges expressing NTD (1-35)-EFGP formed a highly organized capsule despite no differences in cellular composition, suggesting stimulation of collagen deposition by the calreticulin-binding sequence of TSP1. TSP1, recombinant NTD, or a peptide of the TSP1 calreticulin-binding sequence (hep I) increased both collagen expression and matrix deposition by fibroblasts in vitro. TSP1 stimulation of collagen was inhibited by a peptide that blocks TSP1 binding to calreticulin, demonstrating the requirement for cell surface calreticulin. Collagen stimulation was independent of TGF-ß activity and Smad phosphorylation but was blocked by an Akt inhibitor, suggesting that signaling through the Akt pathway is important for regulation of collagen through TSP1 binding to calreticulin. These studies identify a novel function for the NTD of TSP1 as a mediator of collagen expression and deposition during tissue remodeling.

Recent updates in oral terbinafine: its use in onychomycosis and tinea capitis in the US.

Onychomycosis and tinea capitis are prevalent fungal diseases that are difficult to cure and usually require systemic treatment. Onychomycosis has high recurrence rates and can significantly affect a patient's quality of life. Oral terbinafine has been approved for onychomycosis for 20 years in Europe and 15 years in the United States. Over these past 20 years, numerous studies show that oral terbinafine is a safe and efficacious treatment for onychomycosis. More recently, oral terbinafine also has been approved for tinea capitis. Once difficult to treat, terbinafine has revolutionised treatment of these fungal diseases. It has minimal side effects and its limited drug interactions make it an excellent treatment option for patients with co-morbidities. This review discusses oral terbinafine and new insights into the treatment of onychomycosis and tinea capitis. Recent publications have enhanced our knowledge of the mechanisms of oral terbinafine and its efficacy in treating onychomycosis. Oral terbinafine vs. other antifungal therapeutic options are reviewed. Overall, terbinafine remains a superior treatment for dermatophyte infections because of its safety, fungicidal profile, once daily dosing, and its ability to penetrate the stratum corneum.