Serine Protease HtrA1 Associates with Microtubules and Inhibits Cell Migration

Abstract

HtrA1 belongs to a family of serine proteases found in organisms ranging from bacteria to humans. Bacterial HtrA1 (DegP) is a heat shock-induced protein that behaves as a chaperone at low temperature and as a protease at high temperature to help remove unfolded proteins during heat shock. In contrast to bacterial HtrA1, little is known about the function of human HtrA1. Here, we report the first evidence that human HtrA1 is a microtubule-associated protein and modulates microtubule stability and cell motility. Intracellular HtrA1 is localized to microtubules in a PDZ (PSD95, Dlg, ZO1) domain-dependent, nocodazole-sensitive manner. During microtubule assembly, intracellular HtrA associates with centrosomes and newly polymerized microtubules. In vitro, purified HtrA1 promotes microtubule assembly. Moreover, HtrA1 cosediments and copurifies with microtubules. Purified HtrA1 associates with purified ␣-and ␤-tubulins, and immunoprecipitation of endogenous HtrA1 results in coprecipitation of ␣-, ␤-, and ␥-tubulins. Finally, downregulation of HtrA1 promotes cell motility, whereas enhanced expression of HtrA1 attenuates cell motility. These results offer an original identification of HtrA1 as a microtubule-associated protein and provide initial mechanistic insights into the role of HtrA1 in theregulation of cell motility by modulating microtubule stability.

Functional Antagonism between High Temperature Requirement Protein A (HtrA) Family Members Regulates Trophoblast Invasion

“…We reasoned that the secreted HtrA1 and HtrA3 may regulate the invasion of EVT into the decidua by counteracting the HtrA4 activity of EVT. Indeed, the invasion activity of Dox-induced Chien et al (21) have demonstrated that an intracellular form of HtrA1 associates with microtubules and suppresses cell motility. Although HtrA1 contains a signal peptide for secretion, it is not clear how the intracellular form of HtrA1 is trafficked to cytosol.…”

Human High Temperature Requirement Serine Protease A1 (HTRA1) Degrades Tau Protein Aggregates

“…Extracytoplasmic HTRA1 is involved in the homeostasis of the extracellular matrix, and elastin, fibulin 5, nidogen 2, fibronectin, fibromodulin, aggrecan, and decorin have been identified as substrates (12)(13)(14)(15)(16)(17). Intracellular HTRA1 was localized to microtubules and to the nucleus (18,19). Cytoplasmic HTRA1 has been implicated in the degradation of tuberin thereby modulating cell growth and proliferation (20).…”

“…Cytoplasmic HTRA1 has been implicated in the degradation of tuberin thereby modulating cell growth and proliferation (20). Furthermore, microtubule-associated HTRA1 degrades tubulins thereby inhibiting cell migration (18,21). Consequently, HTRA1 has been implicated in several severe pathologies including cancer, age-related macular degeneration, Alzheimer disease (AD), arthritis, and familial ischemic cerebral small vessel disease (12,13,(22)(23)(24)(25)(26).…”

HTRA1 (HtrA serine peptidase 1)

“…However, processed forms of HtrA1 have been found in the cytoplasm and in the nuclear fraction (Clawson et al, 2008;Chien et al, 2009;He et al, 2010).…”