Progranulin is composed of seven repeating cysteine-rich granulin domains. In some cells and tissues, the progranulin is fragmented by proteolysis to generate the granulin modules as individual peptides, which are collectively referred to as granulins. These peptides are often biologically active, but the activity need not be identical to that of the parental progranulin from which they are derived. Thus, some granulin peptides stimulate cell proliferation, as does progranulin itself, while other granulin peptides suppress proliferation. Similarly, some granulin peptides promote inflammation even though progranulin itself suppresses inflammation. Investigating the structural and biological properties of granulin peptides is challenging. Here we discuss methods that employ reversed-phase high-performance liquid chromatography (RP-HPLC) and in some instances size-exclusion high-performance liquid chromatography (SE-HPLC) to isolate granulin peptides from tissues, in particular those that are rich in inflammatory cells such as neutrophils, bone marrow, or hematopoietic organs of teleost fish.
Keywords: Carp spleen; Granulin; High-performance liquid chromatography; Neutrophils; Peptide extraction.