Author ORCID Identifier
0000-0002-3333-175X
Date of Graduation
8-2024
Document Type
Thesis (MS)
Program Affiliation
Cancer Biology
Degree Name
Masters of Science (MS)
Advisor/Committee Chair
Burton Dickey
Committee Member
Michael Tuvim
Committee Member
Jian Hu
Committee Member
Harry Karmouty-Quintana
Committee Member
Roberto Adachi
Abstract
Mucus plays a vital role in shielding the lungs against harmful substances such as particles, pathogens, and chemicals inhaled from the environment. It captures these harmful elements, and ciliary action helps to expel them from the lungs. Paradoxically, malfunctioning of mucus induces the development of various respiratory illnesses, including asthma, cystic fibrosis, chronic obstructive pulmonary disease (COPD), and interstitial lung diseases. Despite extensive research on controlling mucin production and hydration, the process of secretion is not yet fully comprehended.
Mucin undergoes regulated secretion at two rates: a low baseline rate and a high stimulated rate. Over the past 25 years, our lab has discovered and defined that these two rates involve distinct molecular machineries. The exocytosis process is mediated by the collaborative interaction between a SNARE complex and an SM (Sec1/Munc18) protein. One type of SNARE protein, a Vesicle-Associated Membrane Protein (VAMP), has been shown to regulate exocytosis in multiple cell types.
Here, we report that VAMP8 has the highest gene expression among all VAMP isoforms in human airway secretory cells, as revealed by an analysis of a public scRNA-seq database. Using airway epithelium specific deletant mice,
I found that VAMP8 mediates both baseline and stimulated secretion. At the subcellular level, VAMP8 is colocalized on MUC5B-only, MUC5AC-only, and MUC5B/MUC5AC double-positive granules. To identify the VAMP predominately responsible for baseline secretion, we focused on VAMP2 and VAMP3 based on their high expression levels in airway secretory cells and roles in exocytosis in different cell types. No baseline secretion defects were observed in VAMP3 knockout mice. To study VAMP2 and avoid the embryonic lethality in VAMP2 knockout mice, I established airway epithelium specific VAMP2 and VAMP3 double deletant mice that are currently being studied.
This project establishes the role of VAMP8 in mediating baseline and stimulated secretion, highlighting the therapeutic potential of targeting VAMP8 in treating muco-obstructive diseases. The studies on VAMP2 and VAMP3 will contribute to identifying the baseline exocytic machinery.
Keywords
Airway Mucin Secretion, VAMP, SNARE protein