The Transmembrane Serine Protease HAT-like 4 Is Important for Epidermal Barrier Function to Prevent Body Fluid Loss

Abstract

Membrane-bound proteases are essential for epidermal integrity. Human airway trypsin-like protease 4 (HAT-L4) is a type II transmembrane serine protease. Currently, its biochemical property, cellular distribution and physiological function remain unknown. Here we examined HAT-L4 expression and function in vitro and in vivo. In Western analysis, HAT-L4 expressed in transfected CHO cells appeared as a 48-kDa protein. Flow cytometry confirmed HAT-L4 expression on the cell surface with the expected membrane topology. RT-PCR and immunostaining experiments indicated that HAT-L4 was expressed in epithelial cells and exocrine glands in tissues including skin, esophagus, trachea, tongue, eye, bladder, testis and uterus. In the skin, HAT-L4 expression was abundant in keratinocytes and sebaceous glands. We generated HAT-L4 knockout mice by disrupting the Tmprss11f gene encoding HAT-L4. HAT-L4 knockout mice were viable and fertile. No defects were found in HAT-L4 knockout mice in hair growth, wound healing, water repulsion and body temperature regulation. Compared with wild-type controls, HAT-L4-deficient newborn mice had greater body fluid loss and higher mortality in a trans-epidermal body fluid loss test. In metabolic studies, HAT-L4-deficient adult mice drank water more frequently than wild-type controls did. These results indicate that HAT-L4 is important in epidermal barrier function to prevent body fluid loss.

Ectopic expression of human airway trypsin‐like protease 4 in acute myeloid leukemia promotes cancer cell invasion and tumor growth

“…Normally, human HAT-L4 is expressed in epithelial cells and exocrine glands in the skin, esophagus, trachea, testis and placenta. 28,29 By RT-PCR, we did not detect HAT-L4 mRNA expression in peripheral white blood cells or bone marrow cells from normal individuals. Consistently, HAT-L4-deficient mice had normal blood cell counts, including red blood cells, white blood cells and platelets.…”

“…Consistently, HAT-L4-deficient mice had normal blood cell counts, including red blood cells, white blood cells and platelets. 29 The mechanism underlying the ectopic HAT-L4 expression in AML is unclear. Among TTSPs overexpressed in cancer, TMPRSS2 expression in prostate cancer is regulated by an androgen response element in the gene promotor.…”

“…The plasmid expressing human HAT-L4 was described previously. 29 Plasmids expressing HAT-L4 mutants (R and R1) resistant to shRNA targeting ( Figure S1) were made by site-directed mutagenesis. Recombinant HAT-L4 proteins contained a C-terminal V5 tag that allowed detection by an anti-V5 antibody (Invitrogen) in Western blotting.…”

“…1 HAT-L4 is expressed in epithelial cells and exocrine glands in many tissues including the skin, esophagus, trachea, tongue, bladder and uterus. 28,29 In mice, HAT-L4 is dispensable for embryonic development and postnatal hematopoiesis. 29 In high temperatures, HAT-L4-deficient newborn pups were prone to body fluid loss, indicating that HAT-L4 is important for normal epidermal barrier function.…”

“…28,29 In mice, HAT-L4 is dispensable for embryonic development and postnatal hematopoiesis. 29 In high temperatures, HAT-L4-deficient newborn pups were prone to body fluid loss, indicating that HAT-L4 is important for normal epidermal barrier function. 29 Here, we report an unexpected finding of ectopic HAT-L4 expression in bone marrow cells from patients with acute myeloid leukemia (AML), the most common type of acute leukemia in adults.…”