Matriptase Regulates Proliferation and Early, but Not Terminal, Differentiation of Human Keratinocytes

Abstract

Genetic defects in matriptase are linked to two congenital ichthyosis, autosomal recessive ichthyosis with hypotrichosis (ARIH, OMIM 610765) and, ichthyosis, follicular atrophoderma, hypotrichosis, and hypohidrosis (IFAH, OMIM602400). Mouse models with matriptase deficiency indicate an involvement of matriptase in suprabasal keratinocytes in the maintenance of the epidermal barrier. In contrast to what has been reported for mouse skin, we show that in human skin, matriptase is primarily expressed in the basal and spinous keratinocytes, but not in the more differentiated keratinocytes of the granular layer. In addition, matriptase zymogen activation was predominantly detected in the basal cells. Furthermore, using skin organotypic cultures as a model system to monitor the course of human epidermal differentiation, we found elevated matriptase zymogen activation during early stages of epidermal differentiation, coupled with a loss of matriptase expression in the late stages of this process. We also show here that matriptase deficiency in HaCaT cells modestly reduces cell proliferation and temporally affects calcium-induced expression of differentiation markers. These collective data suggests that, unlike mouse matriptase, human matriptase may be involved in regulation of keratinocyte growth and early differentiation, rather than terminal differentiation, providing mechanistic insights for the pathology of the two congenital ichthyoses, ARIH and IFAH.

Matriptase Expression and Zymogen Activation in Human Pilosebaceous Unit

“…In these two types of late-stage differentiated cells of the hair follicle, HAI-1 is expressed at high levels whereas matriptase expression is very low or absent. This expression pattern echoes the expression pattern of HAI-1 in epidermal granular keratinocytes, which are also at a late stage of differentiation and are matriptase-negative (Chen et al, 2013a).…”

“…Furthermore, our studies reveal that the activated form of matriptase is primarily detected in the matrix and basal cells, suggesting that matriptase proteolytic activity is likely to be actively involved in the cellular processes of these proliferative and differentiating cells. This hypothesis is further bolstered by our studies in which shRNA-induced suppression of matriptase expression in human keratinocytes decreased both cell proliferation and the expression of differentiation markers (Chen et al, 2013a).…”

“…The role of antithrombin in the control of matriptase activity appears to be augmented in human keratinocytes relative to other epithelial systems. In keratinocytes, the levels of antithrombin bound to the cell surface is inversely correlated with the levels of active matriptase shed to the extracellular milieu (Chen et al, 2013b). In the mouse, HAI-2 has been reported to be involved in the control of matriptase (Szabo et al, 2008).…”

Selective Inhibition of Prostasin in Human Enterocytes by the Integral Membrane Kunitz-Type Serine Protease Inhibitor HAI-2

“…The human prostasin mAbs YL11 and YL89 were generated using milk-derived prostasin-HAI-1 complexes as immunogen as described previously [11]. The human matriptase mAb M24 was used to detect matriptase zymogen and activated forms in complexes with protease inhibitors [25,26]. HAI-1 mAb M19, HAI-2 mAb DC16, prostasin mAb YL11, and matriptase mAb 21-9 [27] were also immobilized to Sepharose beads at 5 mg/ml gel, according the manufacturer's instruction (GE Healthcare Life Science, Marlborough, MA).…”

Matriptase and prostasin are expressed in human skin in an inverse trend over the course of differentiation and are targeted to different regions of the plasma membrane

“…In spite of the above-mentioned functional relationship, there seems to be some evolutionary divergence between human and mouse with regard to matriptase, which is expressed primarily in the basal and spinous layers of the human epidermis and participates in the control of epidermal proliferation and early differentiation (Chen et al, 2013a). The pattern of human matriptase expression in vivo with differentiation-associated down-regulation has been also observed in human hair follicles, sebaceous glands (Wu et al, 2013), and replicated in the organotypic skin raft model (Chen et al, 2013a).…”