# The Heat Shock Protein 60 and Pap1 Participate in the _Sporothrix schenckii_-Host Interaction
## 4 Discussion
Heat shock proteins are highly conserved in all living organisms and upregulated in response to different stress conditions, playing important roles in cell homeostasis [81]. Their main function is proper protein folding, unfolding, and translocation and the assembly and disassembly of protein complexes. Members of the Hsp60 family, also called mitochondrial chaperones, assist in the refolding of denatured proteins under stress conditions, as well as in the folding of newly synthesized proteins and as a transporter of proteins targeted to different cellular compartments, and are preferentially found in the mitochondria and cytoplasm [82; 83]. In addition to these canonical functions, members of the Hsp60 family of proteins werealso reported to be highly immunogenic in different pathogenic organisms, including _H. capsulatus_[36], _P. brasiliensis_, and _Paracoccidioides lutzii_[84; 85], and were also localized within the fungal cell wall [38]. The expression patterns of _S. schenckii HSP60_, named upregulation in yeast-like cells and fungal cells co-incubated with human cells, agreed with previous observations in _Aspergillus fumigatus_, _Aspergillus terreus_, _Scedosporium apiospenum_, _C. albicans_, _Penicillium chrysogenum_, _P. brasiliensis_, and _Trichophyton metrasophytes_, where exposure to high temperatures caused an _HSP60_ temperature-dependent upregulation [38; 86]. For the case of Pap1, as mentioned, this protein has putative homologs in _O. picaea_ and _G. clavigena_, and in the former, the protein was predicted to be at the cell surface. In addition, these two proteins, along with Pap1, were predicted to contain disordered domains and were considered intrinsically disordered proteins ([[https://iupred2a.elte.hu](https://iupred2a.elte.hu)]([https://iupred2a.elte.hu](https://iupred2a.elte.hu)); accessed on 5 October 2018) [50]. These kinds of proteins are characterized by the lack of a well-defined folding and structure under physiological conditions, and thus, are considered out of the structure-function paradigm, and their function cannot be predicted by structural motifs [87; 88]. Some of the functions already demonstrated for these proteins include molecular recognition and binding to other molecules, which are consequences of the direct transition from ordered to disordered flexible regions [88]. Interestingly, many moonlighting proteins are also intrinsically disordered proteins and participate in protein-protein interactions [89]. We observed that most of the main PRM proteins given in Table 1 were predicted to be long disordered proteins with scores higher than 0.5 (data not shown). These proteins are heat shock 70 kDa protein 1/8, elongation factor 1-alpha, GPI-anchored cell wall beta-1,3-endoglucanase EgIC, large subunit ribosomal protein LP2, AMPK1_CBM domain-containing protein, molecular chaperone DnaK, glucose-repressible protein, peptidyl-prolyl cis-trans isomerase, large subunit ribosomal protein LPI, sphingolipid long-chain base-responsive protein, acetyltransferase component of pyruvate dehydrogenase complex, mismatched base pair and cruciform DNA recognition protein, aconitate hydratase mitochondrial, cytochrome C oxidase subunit 5b, actin beta/gamma 1, and the uncharacterized proteins SPSK_04236, SPSK_05930, SPSK_01041, SPSK_02764, and SPSK_06559. The proteins glyceraldehyde-3-phosphate dehydrogenase, ATP synthase subunit beta, and 2-phosphoglycerate dehydatase were predicted to be short disordered, while Hsp60 and aldehyde dehydrogenase (NAD+) were predicted to be ordered/structured proteins (data not shown). These observations agreed with our suggestion that these proteins are likely to be moonlight proteins. Moreover, the _PAP1_ expression indicated is upregulated in yeast-like cells and when interacting with host cells, adding further evidence to suggest it could have a role during the _S. schenckii_-host interaction. The findings presented here showed Hsp60 and Pap1 are PRM members and are likely moonlighting proteins that participate in the adhesion of the ECM to components.