# NKLAM: An RBR E3 Ubiquitin Ligase Essential for Regulation of Innate Immunity

> **NIH VA I01** · ST. LOUIS VA MEDICAL CENTER · 2020 · —

## Abstract

The innate immune system serves is the first response to diseased cells and infectious agents. Natural
Killer (NK) cells and macrophages are primary components of this system. Although their functions differ, they
both require the expression of NKLAM (Natural Killer Lytic-Associated Molecule) for optimal function.
Accordingly, elucidating the role of NKLAM in innate immunity has important biological and clinical significance.
 NKLAM is up-regulated in NK cells upon exposure to tumor cells or cytokines that activate cytolytic
function. NKLAM is up-regulated in macrophages upon exposure to bacteria or pro-inflammatory cytokines. We
generated NKLAM-deficient (KO) mice; they have less NK activity than WT (wild type) mice. They exhibit greater
tumor growth, tumor dissemination and metastasis than WT mice. NKLAM KO mice also have defects in
macrophage anti-bacterial function in vivo and in vitro.
 NKLAM is a member of a small, highly conserved, unique group of RING-in between-RING (RBR) E3
ubiquitin ligases. RBR E3 ubiquitin ligases play a key role in cellular physiology and are involved in the
pathogenesis of many diseases, including cancer, autoimmune diseases and neurological disorders. There is
great interest in drug discovery to target them. We identified key potential substrates of NKLAM-mediated
ubiquitination, including the transcription factors STAT1 and c-myc, Bcl-2 and UCKL-1 (uridine cytidine kinase
like-1), a protein that promotes tumor growth. The central nature of these substrates in cell signaling, growth and
survival suggests that drug modulation of NKLAM has significant potential for treating cancer and infectious
diseases.
 We found that activated NK cells releases exosomes containing NKLAM. NKLAM+ exosomes promote
tumor cell death in vitro. Preliminary data indicate that NKLAM+ exosomes enter target cells and deliver NKLAM.
Important unanswered questions that will be addressed are the effect of NKLAM on critical substrates in effector
cells and in target cells.
 The role of NKLAM in macrophages is undoubtedly different from its role in NK cells in that killing of
bacteria occurs intracellularly. Our ongoing studies suggest that NKLAM modulates the signaling events that
activate the macrophage anti-bacterial program. A key regulator of this pathway is STAT1.
 We will test the hypothesis that the E3 ubiquitin ligase activity of NKLAM plays a role in the anti-tumor
and anti-microbial functions of NK cells and macrophages with the following three interconnected but
independent aims:
 Aim 1: Elucidate the role of NKLAM in exosome-mediated killing of tumor cells. We will test the
hypothesis that upon entry of NK-derived exosomes containing NKLAM into tumor cells, NKLAM interacts with
critical substrates, resulting in cell death. We will test the ability of exosomes from NKLAM WT, NKLAM KO and
NKLAM ligase defective NK cells to kill tumor cells in vivo using a mouse model of multiple myeloma, a disease
increasing in frequency, especially i...

## Key facts

- **NIH application ID:** 9898218
- **Project number:** 5I01BX000705-08
- **Recipient organization:** ST. LOUIS VA MEDICAL CENTER
- **Principal Investigator:** JACKI KORNBLUTH
- **Activity code:** I01 (R01, R21, SBIR, etc.)
- **Funding institute:** VA
- **Fiscal year:** 2020
- **Award amount:** —
- **Award type:** 5
- **Project period:** 2012-04-01 → 2021-09-30

## Primary source

NIH RePORTER: https://reporter.nih.gov/project-details/9898218

## Citation

> US National Institutes of Health, RePORTER application 9898218, NKLAM: An RBR E3 Ubiquitin Ligase Essential for Regulation of Innate Immunity (5I01BX000705-08). Retrieved via AI Analytics 2026-05-24 from https://api.ai-analytics.org/grant/nih/9898218. Licensed CC0.

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