Myosin VIIA is specifically associated with calmodulin and microtubule-associated protein-2B (MAP-2B).

Myosin VIIA is a motor molecule with a conserved head domain and tail region unique to myosin VIIA, which probably defines its unique function in vivo. In an attempt to further characterize myosin VIIA function we set out to identify molecule(s) that specifically associate with it. We demonstrate that 17 and 55 kDa proteins from mouse kidney and cochlea co-purify with myosin VIIA on affinity columns carrying immobilized anti-myosin VIIA antibody. N-terminal sequencing and immunoblotting analysis identified the 17 kDa protein as calmodulin, whereas MS and immunoblotting analysis identified the 55 kDa protein as microtubule-associated protein-2B (MAP-2B). Myosin VIIA can also be co-immunoprecipitated from kidney homogenate using anti-calmodulin or anti-MAP2 (recognizing isoforms 2A and 2B) antibodies, confirming the strong association between calmodulin and myosin VIIA and between MAP-2B and myosin VIIA. Myosin VIIA binds to calmodulin with an apparent K(d) of 10(-9) M. Scatchard analysis of the binding of myosin VIIA to MAP-2B provided evidence for two binding sites, with K(d) values of 10(-10) and 10(-9) M, which have been mapped to medial and C-terminal tail domains of myosin VIIA. The characterization of the interaction of calmodulin and MAP-2B with myosin VIIA provides new insights into the function of myosin VIIA.

Effect of a fluorinated pyrimidine on cachexia and tumour growth in murine cachexia models: relationship with a proteolysis inducing factor.

The fluorinated pyrimidine nucleoside, 5'-deoxy-5-fluorouridine (5'-dFUrd) has been shown to effectively attenuate the progress of cachexia in the murine adenocarcinomas MAC16 and colon 26 as well as in the human uterine cervical carcinoma xenograft, Yumoto. Although concomitant inhibition of tumour growth was observed in all three models this was not sufficient to account for the preservation of body weight. An attempt has been made to correlate the anti-cachectic activity of 5'-dFUrd with the presence of a tumour produced proteolysis-inducing factor (PIF), thought to be responsible for the development of cachexia in the MAC16 model. Two variants of colon 26 adenocarcinoma were employed, clone 20 which produces profound cachexia, and clone 5 which produces no change in body weight in recipient animals. Mice bearing the colon 26, clone 20 variant showed evidence for the presence of PIF in tumour, serum and urine, while there was no evidence for the presence of PIF in tumour or body fluids of mice bearing the clone 5 tumours. Treatment of animals bearing the clone 20 variant with 5'-dF Urd led to the disappearance of PIF from the tumour, serum and urine concomitant with the attenuation of the development of cachexia. The human cervical carcinoma, Yumoto, which also induced cachexia in recipiant animals, showed expression of PIF in tumour, serum and urine in control and vehicle-treated mice, but was absent in mice treated with 5'-dFUrd. Thus in these experimental models cachexia appears to be correlated with the presence of PIF.

Characteristics of patients with pancreatic cancer expressing a novel cancer cachectic factor.

BACKGROUND: Recently a novel tumour-derived cachectic factor was identified in the murine MAC16 colonic adenocarcinoma model of cachexia. This factor, provisionally named proteolysis-inducing factor (PIF), was subsequently identified in the urine of weight-losing patients with cancer but not in the urine of weight-stable patients with cancer or weight-losing controls with benign disease. This study determined the nutritional characteristics of patients with pancreatic cancer who excrete PIF in the urine and investigated the relationship between PIF and the acute-phase protein response. METHODS: PIF was isolated from urine by precipitation and ultrafiltration and was then identified by Western blotting of nitrocellulose membranes using a previously developed monoclonal antibody. Full nutritional assessment of patients was undertaken at the same time as urine collection. RESULTS: PIF was detected in the urine of 80 per cent of patients (n = 55). These patients had a significantly greater total weight loss and rate of weight loss than patients whose urine did not contain PIF (median 12.5 (range 4-43) kg versus 4.5 (0-14) kg; P < 0.0002). No association was evident between the presence of PIF in patients' urine and serum C-reactive protein (CRP) concentration. Furthermore, the accelerated weight loss associated with PIF expression also appeared to be independent of the acute-phase response. Overall the presence of PIF was not associated with reduced survival, although the previously reported association between raised CRP concentration and poor prognosis was confirmed. CONCLUSION: PIF is associated with an accelerated rate of weight loss in patients with a tumour of the pancreatic head. This observation appears to be independent of the effect of an increased hepatic acute-phase protein response.

Role of a proteolysis-inducing factor (PIF) in cachexia induced by a human melanoma (G361).

Human melanoma, G361, which induces cachexia in nude mice, has been shown to produce a proteolysis-inducing factor (PIF) of Mr 24000, which is immunologically identical to that isolated from a cachexia-inducing murine tumour (MAC16). Biosynthetic labelling of G361 cells using a combination of [35S]sulphate and [6-3H]glucosamine gave a single component of Mr 24000 after affinity chromatography employing a murine monoclonal antibody. The material contained both radiolabels and, after digestion with peptide N-glycosidase F, two fragments were produced of Mr 14000 and 10000 also containing both radiolabels. Digestion with O-glycosidase produced three fragments of Mr 14000, 6000 and 4000, the first two of which contained both radiolabels, while the third only contained 3H. This digestion pattern is the same as that previously observed with PIF from the MAC16 tumour and is commensurate with one N-linked sulphated oligosaccharide chain of Mr 10000, one O-linked sulphated oligosaccharide chain of Mr 6000 and a central polypeptide chain of Mr 4000 with some residual carbohydrate. When PIF from G361 cells was administered to female NMRI mice (20 g) a pronounced depression of body weight (1.36+/-0.36 g; P < 0.0001 from control) was observed over a 24 h period without a decrease in either food or water consumption. Body composition analysis showed a significant decrease in the non-fat carcass mass without a change in carcass fat or body water. This result suggests that depletion of lean body mass in mice bearing G361 melanoma arises from the production of PIF.

Purification and characterization of a tumor lipid-mobilizing factor.

Cancer patients with weight loss showed urinary excretion of a lipid-mobilizing factor (LMF), determined by the ability to stimulate lipolysis in isolated murine epididymal adipocytes. Such bioactivity was not detectable in the urine of cancer patients without weight loss or in normal subjects. The LMF was purified using a combination of ion exchange, exclusion, and hydrophobic interaction chromatographies to give a single component of apparent Mr 43,000, which showed homology in amino acid sequence with human plasma Zn-alpha2-glycoprotein. Both substances showed the same mobility on denaturing and nondenaturing gels and the same chymotrypsin digestion pattern, both stained heavily for carbohydrate, and they showed similar immunoreactivity. Polyclonal antisera to human plasma Zn-alpha2-glycoprotein was also capable of neutralization of the bioactivity of human LMF in vitro. Using competitive PCR to quantify expression of Zn-alpha2-glycoprotein, we found that only those tumors that were capable of producing a decrease in carcass lipid expressed mRNA for Zn-alpha2-glycoprotein. These results provide strong evidence to suggest that tumor production of Zn-alpha2-glycoprotein is responsible for the lipid catabolism seen in cancer patients.

Structural analysis of a tumor-produced sulfated glycoprotein capable of initiating muscle protein degradation.

A material of Mr 24,000 has been isolated from a cachexia-inducing mouse tumor (MAC16) and shown to initiate protein degradation in isolated gastrocnemius muscle. Biological activity was destroyed by preincubation with peptide N-glycosidase F (PNGase F) and endo-alpha-N-acetylgalactosaminidase (O-glycosidase) but not by neuraminidase or trypsin. Antibody reactivity was destroyed by treatment with periodate, indicating carbohydrate moieties to be the antigenic determinants. Antigenic activity was also reduced by treatment with PNGase F and O-glycosidase and was completely destroyed by treatment with chondroitinase ABC but was unaffected by treatment with either trypsin or chymotrypsin, confirming that the N- and O-linked sulfated oligosaccharide chains were both the antigenic and biological determinants. Biosynthetic labeling of MAC16 cells using a combination of [35S]sulfate and [6-3H]GlcN gave a single component of Mr 24,000 containing both radiolabels. Similar material could not be isolated from a cell line (MAC13) originating from a tumor that does not cause cachexia in vivo. Digestion of 3H/35S material with PNGase F produced two fragments of Mr 14,000 and 10,000 containing both radiolabels, and digestion with O-glycosidase produced three fragments of Mr 14,000, 6,000, and 4, 000, the first two contained both radiolabels and the third contained only 3H. Digestion of the fragment of Mr 14,000 released by PNGase F with O-glycosidase also gave fragments of Mr 6,000 and 4, 000. The products from both digestions were acidic as determined by anion exchange chromatography on DEAE-cellulose. The negative charge on the fragment of Mr 4,000 was removed by treatment with alkaline phosphatase. This suggests that the charge originated from phosphate residues, and this has been confirmed by biosynthetic labeling of MAC16 cells with [32P]orthophosphate, where radiolabel was incorporated into material of Mr 24,000 and into the fragment of Mr 4,000 after treatment with O-glycosidase. To determine the size of the polypeptide core MAC16 cells were biosynthetically labeled with L-[2,5-3H]His which after chemical deglycosylation produced a major component of Mr 4,000. These results suggest a model for the Mr 24, 000 material consisting of a central polypeptide chain of Mr 4,000 and with phosphate residues that may be attached to the polypeptide or a short oligosaccharide chain containing GlcN, one O-linked sulfated oligosaccharide chain containing GlcN, and of Mr 6,000 and one N-linked sulfated oligosaccharide chain of Mr 10,000 also containing GlcN. Neither chain was cleaved into disaccharides with chondroitinase ABC, suggesting that the material is a sulfated glycoprotein.

Induction of cachexia in mice by a product isolated from the urine of cachectic cancer patients.

Urine from cancer patients with weight loss showed the presence of an antigen of M(r) 24,000 detected with a monoclonal antibody formed by fusion of splenocytes from mice with cancer cachexia. The antigen was not present in the urine of normal subjects, patients with weight loss from conditions other than cancer or from cancer patients who were weight stable or with low weight loss (1 kg month(-1)). The antigen was present in the urine from subjects with carcinomas of the pancreas, breast, lung and ovary. The antigen was purified from urine using a combination of affinity chromatography with the mouse monoclonal antibody and reversed-phase high-performance liquid chromotography (HPLC). This procedure gave a 200,000-fold purification of the protein over that in the original urine extract and the material isolated was homogeneous, as determined by silver staining of gels. The N-terminal amino acid sequence showed no homology with any of the recognized cytokines. Administration of this material to mice caused a significant (P<0.005) reduction in body weight when compared with a control group receiving material purified in the same way from the urine of a normal subject. Weight loss occurred without a reduction in food and water intake and was prevented by prior administration of the mouse monoclonal antibody. Body composition analysis showed a decrease in both fat and non-fat carcass mass without a change in water content. The effects on body composition were reversed in mice treated with the monoclonal antibody. There was a decrease in protein synthesis and an increase in degradation in skeletal muscle. Protein degradation was associated with an increased prostaglandin E2 (PGE2) release. Both protein degradation and PGE2 release were significantly reduced in mice pretreated with the monoclonal antibody. These results show that the material of M(r) 24,000 present in the urine of cachectic cancer patients is capable of producing a syndrome of cachexia in mice.

Catabolic factors in cancer cachexia.

A lipid mobilizing factor has been purified from a cachexia-inducing mouse colon adenocarcinoma (MAC16) using a combination of ion exchange (Mono Q), exclusion (Superose) and reverse phase hydrophobic chromatography. The purification process led to a 3,500-fold increase in the specific activity. Serum from mice bearing the MAC16 tumour contained antibodies reactive with fractions containing lipid mobilizing activity and detectable as a 24 kDa immunoreactive band on Western blotting. Serum from mice transplanted with a related tumour, MAC13, not producing cachexia, did not contain antibodies. A similar immunoreactive band was detectable in the urine of patients with cancer cachexia, but was absent from the urine of normal subjects. A monoclonal antibody produced by fusion of splenocytes from mice bearing the MAC16 tumour with mouse Balb/c myeloma cells attenuated the development of cachexia in mice transplanted with the MAC16 tumour and inhibited tumour growth. These results suggest that the M(r) 24 kDa antigen may be important in tumour growth and cachexia.

Induction of muscle protein degradation and weight loss by a tumor product.

Splenocytes from mice bearing a cachexia-inducing tumor (MAC16) have been fused with mouse myeloma cells to produce hybridomas, which have been cloned to produce antibody reactive to a material which copurified with a lipid-mobilizing factor isolated from the same tumor. The monoclonal antibody has been used to investigate factors potentially involved in the development of cachexia. The major protein detectable by immunoprecipitation of a partially purified lipid-mobilizing factor was M(r) 69,000, whereas Western blotting showed two bands of M(r) 69,000 and M(r) 24,000. Although the monoclonal antibody did not neutralize lipid-mobilizing activity in an in vitro assay, it did neutralize a serum factor capable of protein degradation in isolated gastrocnemius muscle. Affinity purification of MAC16 tumor homogenates using the monoclonal antibody yielded two immunoreactive bands of M(r) 69,000 and M(r) 24,000, which were further fractionated on a hydrophobic column (C8). This material was capable of inducing tyrosine release from isolated gastrocnemius muscle, and the effect could be blocked with the monoclonal antibody. The two immunoreactive bands from the hydrophobic column were capable of inducing weight loss in mice, whereas nonimmunoreactive fractions had no effect on body weight. The M(r) 24,000 species had a unique amino acid sequence, whereas the M(r) 69,000 species gave the same sequence as the M(r) 24,000 material, together with that for albumin. The M(r) 24,000 species contained carbohydrate, and lectin blotting showed a strong reaction with wheat germ and Erythrina crystagalli agglutinins. This suggests that the material is a glycoprotein or proteoglycan that shows strong binding affinity for albumin, possibly through the carbohydrate residues.

Purification and characterization of a lipid-mobilizing factor associated with cachexia-inducing tumors in mice and humans.

A scheme is described for the purification of a lipid-mobilizing factor from a cachexia-inducing murine tumor (MAC16) using a combination of ion exchange (Mono Q), exclusion (Superose), and hydrophobic (C8) chromatography. This process yields an active material with an apparent molecular weight of 24,000 with an overall purification of 3,500 from the tumor homogenate and representing 0.005% of the total protein present. The material tends to aggregate to high molecular mass, is acidic (pI < 4), and displays heterogeneity of charge as evidenced by a broad elution profile on ion exchange and exclusion chromatography and multiple peaks on hydrophobic columns. The purified material was heat and alkali (pH 10.4) labile and activity could be completely inhibited by sulfatase, suggesting that the negative charge could arise from sulfate residues. There was no evidence that the material possessed triglyceride lipase activity. Animals transplanted with the MAC16 tumor and with a delayed weight loss contained in their serum antibodies that recognized a M(r) 24,000 band on Western blots. This material copurified with the lipid-mobilizing factor. Such antibodies were not present in the serum of mice transplanted with the MAC13 tumor, which does not induce cachexia, suggesting that the antibodies were directed to the induction of cachexia rather than the tumor itself. Urine from patients with cancer cachexia also contained a lipid-mobilizing factor which adhered to DEAE-cellulose and gave an apparent M(r) of 24,000 by exclusion chromatography. Western blotting using serum from MAC16 tumor-bearing animals showed the presence of a band of M(r) 24,000 in such fractions, which was not detected using serum from mice bearing the MAC13 tumor. This band was not present in Western blots of urine from normal subjects. The fact that serum from mice bearing the MAC16 tumor can detect the human lipid-mobilizing activity suggests a high degree of structural similarity between the two and raises the possibility that cachexia in humans may be caused by the same species as in the mouse.