Human pre-interleukin 1 alpha and beta: structural features revealed by limited proteolysis

Area of Science:

• Biochemistry
• Molecular Biology
• Immunology

Background:

• Precursor forms of interleukin-1 alpha and beta (pre IL-1 alpha and beta) undergo proteolytic processing to yield mature, extracellular cytokines.
• Pre IL-1 alpha is known to be biologically active, suggesting additional functions for proteolytic processing beyond simple activation.

Purpose of the Study:

• To investigate whether structural stabilization is associated with the proteolytic processing of pre IL-1 alpha and beta.
• To elucidate the structural features of pre IL-1 alpha and beta that contribute to their processing.

Main Methods:

• Limited proteolysis using trypsin and V8 protease.
• Immunoprecipitation with antibodies targeting the NH2-terminal or COOH-terminal halves of pre IL-1 alpha and beta.

Main Results:

• Both trypsin and V8 protease preferentially digested the NH2-terminal halves of pre IL-1 alpha and beta, generating more stable "mature" forms.
• Trypsin and V8 protease produced a fragment of similar size to mature IL-1 alpha from pre IL-1 alpha.
• Trypsin yielded fragments smaller than mature IL-1 beta from pre IL-1 beta, whereas V8 protease generated a fragment similar in size to mature IL-1 beta.
• Mature IL-1 beta, once released, demonstrated resistance to trypsin digestion.

Conclusions:

• Proteolytic processing of pre IL-1 alpha and beta leads to structurally stabilized mature forms.
• The differential susceptibility of pre IL-1 alpha and beta to proteases suggests distinct processing pathways and structural characteristics.
• Stabilization of mature IL-1 beta confers resistance to further degradation by proteases like trypsin.