Calcium-binding protein, spermatid-specific 1 is expressed in human salivary glands and contains an anti-inflammatory motif

Abstract

Salivary glands are involved in the production and exocrine and endocrine secretion of biologically active proteins, polypeptides, and hormones involved in growth and differentiation, homeostasis, and digestion. We have previously studied the prohormone submandibular rat 1 (SMR1), product of the Vcsa1 gene, which is highly expressed in the testes and salivary glands of rats, and can be cleaved to produce polypeptides with analgesic, erectile function, and anti-inflammatory activities. Humans lack the Vcsa1 gene, but homologous sequences and functions for analgesia and erectile function exist in the human genes Prol1, SMR3a, and SMR3b located on the human chromosomal region close to where Vcsa1 lies in the rat. Here we show the human protein calcium-binding protein spermatid-specific 1 (CABS1) contains a similar sequence to the anti-inflammatory sequence in rat SMR1, thus CABS1 may be another human gene with homologous function to Vcsa1. Using Western blot and PCR, we discovered that the human protein CABS1, previously thought to only be expressed in the testes, is also expressed in the salivary glands and lung, in a tissue-specific manner. Peptides derived from CABS1 were tested in an in vivo mouse model of lipopolysaccharide (LPS)-induced neutrophilia and an ex vivo rat model of antigen-induced intestinal anaphylaxis and significantly reduced both neutrophil accumulation in bronchoalveolar lavage fluid and antigen-induced ileal contractions, respectively. Thus human CABS1 has a peptide motif homologous to the anti-inflammatory peptide sequence of rat SMR1. Whether this similarity of CABS1 extends to the neuroendocrine regulation of the anti-inflammatory activity seen for SMR1 remains to be determined.

Structural and posttranslational analysis of human calcium‐binding protein, spermatid‐associated 1

“…In agreement with this observation, we have shown that N-or O-glycanase treatment does not alter CABS1 M r in SDS-PAGE, suggesting that glycosylation events do not explain the discrepancies in M r of the protein. 12 Other posttranslational modifications like phosphorylation have been observed for CABS1 in vivo. 36 However, a single phosphorylation event only contributes 80 Da in M r .…”

“…Interestingly, a model of intestinal anaphylaxis showed that "TxI" was not necessary to elicit anti-inflammatory activity. 12 We observed that "FELL" elicited this activity and postulated that this tetrapeptide contains the core anti-inflammatory component. 12 Moreover, a Shannon entropy analysis indicates that the anti-inflammatory sequence displays noticeably lower level of entropy in primates ( Figure S1).…”

“…The anti-inflammatory sequence TDIFELL was first identified in humans and experiments showed that FELL also had anti-inflammatory activity. 12 Thus, we categorized species containing FELL within the TxIFELL peptide as ones with the anti-inflammatory domain. Out of the 72 analyzed species, only 14 contain the putative antiinflammatory domain "TxIFELL," all of which were primates of the infraorder Simiiformes (Figure 3).…”

“…39 The presence of neutrophil elastase in the oral cavity makes it a likely candidate for hCABS1 processing. We previously reported the presence of several hCABS1 forms in saliva using immunodetection by Western blot 12,13,40 and capillary nano-immunoassay. 41 To better understand the complex pattern of likely P1 residues for neutrophil elastase shown in Figure 4B, we calculated the "20 amino acid moving average" of P1 sites along the hCABS1 sequence ( Figure 4C).…”

“…12 Interestingly, several molecular forms of hCABS1 have been found in human testes, lungs, salivary gland extracts, and saliva. 12,13 To determine if hCABS1 is under neural control as SMR1 is, we investigated the relationship between levels of molecular forms of hCABS1 in saliva during acute and prolonged stress. 13 We detected a 27 kDa form of hCABS1 in saliva that correlated with increased self-perceived stress, and smaller molecular forms (≤20 kDa) associated with resilience to stress, data suggesting that hCABS1 is a biomarker of stress.…”