Differences in targeting and secretion of cathepsins B and L by BALB/3T3 fibroblasts and Moloney murine sarcoma virus-transformed BALB/3T3 fibroblasts

Charles Achkar, Qiuming Gong, Allen Frankfater, Andrew S. Bajkowski

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Abstract

BALB/3T3 fibroblasts (3T3) were observed to secrete latent, pepsin-activatable forms of cathepsin B and cathepsin L as well as an active form of β-glucuronidase when cultured in the absence of serum. The secretion of these proteins was stimulated by the cation ionophore monensin: cathepsin B, 4.3-fold; cathepsin L, 7.2-fold; and β-glucuronidase, 3.1-fold. These increases were accompanied by a 50% decline in cellular levels of the active forms of these enzymes and by the cellular accumulation of latent forms of cathepsin B and cathepsin L. Latent forms of β-glucuronidase were not detected. In contrast, Moloney murine sarcoma virus-transformed BALB/3T3 fibroblasts (MMSV) secreted greatly increased amounts of latent cathepsin B (17-fold) and latent cathepsin L (27-fold), and moderately increased amounts of active β-glucuronidase (2-fold) in a manner which was not further increased by monensin. The increased monensin-insensitive secretion of these lysosomal enzymes by MMSV cells may be due to a transformation-induced decrease in mannose 6-phosphate receptors. Thus, 3T3 cells bound the neoglycoconjugate pentamannosyl 6-phosphate-bovine serum albumin at 4°C in a pentamannosyl 6 phosphate and mannose 6-phosphate-inhibitable manner, whereas MMSV cells showed no measurable cell surface mannose 6-phosphate receptor binding activity.

Original languageEnglish (US)
Pages (from-to)13650-13654
Number of pages5
JournalJournal of Biological Chemistry
Volume265
Issue number23
StatePublished - Aug 15 1990
Externally publishedYes

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Moloney murine sarcoma virus
Cathepsin L
Cathepsin B
Glucuronidase
Fibroblasts
Viruses
Monensin
IGF Type 2 Receptor
L Forms
3T3 Cells
Pepsin A
Ionophores
Enzymes
Bovine Serum Albumin
Cations
Phosphates
Serum
Proteins

ASJC Scopus subject areas

  • Biochemistry

Cite this

Differences in targeting and secretion of cathepsins B and L by BALB/3T3 fibroblasts and Moloney murine sarcoma virus-transformed BALB/3T3 fibroblasts. / Achkar, Charles; Gong, Qiuming; Frankfater, Allen; Bajkowski, Andrew S.

In: Journal of Biological Chemistry, Vol. 265, No. 23, 15.08.1990, p. 13650-13654.

Research output: Contribution to journalArticle

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abstract = "BALB/3T3 fibroblasts (3T3) were observed to secrete latent, pepsin-activatable forms of cathepsin B and cathepsin L as well as an active form of β-glucuronidase when cultured in the absence of serum. The secretion of these proteins was stimulated by the cation ionophore monensin: cathepsin B, 4.3-fold; cathepsin L, 7.2-fold; and β-glucuronidase, 3.1-fold. These increases were accompanied by a 50{\%} decline in cellular levels of the active forms of these enzymes and by the cellular accumulation of latent forms of cathepsin B and cathepsin L. Latent forms of β-glucuronidase were not detected. In contrast, Moloney murine sarcoma virus-transformed BALB/3T3 fibroblasts (MMSV) secreted greatly increased amounts of latent cathepsin B (17-fold) and latent cathepsin L (27-fold), and moderately increased amounts of active β-glucuronidase (2-fold) in a manner which was not further increased by monensin. The increased monensin-insensitive secretion of these lysosomal enzymes by MMSV cells may be due to a transformation-induced decrease in mannose 6-phosphate receptors. Thus, 3T3 cells bound the neoglycoconjugate pentamannosyl 6-phosphate-bovine serum albumin at 4°C in a pentamannosyl 6 phosphate and mannose 6-phosphate-inhibitable manner, whereas MMSV cells showed no measurable cell surface mannose 6-phosphate receptor binding activity.",
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