Fungal lectin MpL enables entry of protein drugs into cancer cells and their subcellular targeting.

Simon Žurga,Jerica Sabotič,Janko Kos,Milica Perišić Nanut

doi:10.18632/oncotarget.15849

Simon Žurga, Jerica Sabotič + Show 2 more

Open Access

https://doi.org/10.18632/oncotarget.15849

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Abstract

Lectins have been recognized as promising carrier molecules for targeted drug delivery. They specifically bind carbohydrate moieties on cell membranes and trigger cell internalization. Fungal lectin MpL (Macrolepiota procera lectin) does not provoke cancer cell cytotoxicity but is able to bind aminopeptidase N (CD13) and integrin α3β1, two glycoproteins that are overexpressed on the membrane of tumor cells. Upon binding, MpL is endocytosed in a clathrin-dependent manner and accumulates initially in the Golgi apparatus and, finally, in the lysosomes. For effective binding and internalization a functional binding site on the α-repeat is needed. To test the potential of MpL as a carrier for delivering protein drugs to cancer cells we constructed fusion proteins consisting of MpL and the cysteine peptidase inhibitors cystatin C and clitocypin. The fused proteins followed the same endocytic route as the unlinked MpL. Peptidase inhibitor-MpL fusions impaired both the intracellular degradation of extracellular matrix and the invasiveness of cancer cells. MpL is thus shown in vitro to be a lectin that can enable protein drugs to enter cancer cells, enhance their internalization and sort them to lysosomes and the Golgi apparatus.

Highlights

Lectins are a structurally diverse group of proteins that and reversibly bind to carbohydrates
Fungal lectin MpL (Macrolepiota procera lectin) does not provoke cancer cell cytotoxicity but is able to bind aminopeptidase N (CD13) and integrin α3β1, two glycoproteins that are overexpressed on the membrane of tumor cells
MpL bound to the surface of HeLa and MCF10A neoT cells almost immediately after being added to the cell culture medium and, after 15 minutes, the lectin could already be observed inside the cells (Figure 1, Supplementary Figure 1)

Summary

Introduction

Lectins are a structurally diverse group of proteins that and reversibly bind to carbohydrates. They act as recognition and adhesion molecules and as signal transducers involved in a plethora of physiological functions [1, 2]. Fungal lectins differ from their counterparts from other species in their unique structures and binding specificities [6]. They have shown to be very stable proteins, resistant to changes in pH and temperature as well as to proteolytic digestion, which strengthens their potential for application in biotechnology and medicine.

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